diff --git "a/venv/lib/python3.10/site-packages/sympy/logic/boolalg.py" "b/venv/lib/python3.10/site-packages/sympy/logic/boolalg.py" new file mode 100644--- /dev/null +++ "b/venv/lib/python3.10/site-packages/sympy/logic/boolalg.py" @@ -0,0 +1,3565 @@ +""" +Boolean algebra module for SymPy +""" + +from collections import defaultdict +from itertools import chain, combinations, product, permutations +from sympy.core.add import Add +from sympy.core.basic import Basic +from sympy.core.cache import cacheit +from sympy.core.containers import Tuple +from sympy.core.decorators import sympify_method_args, sympify_return +from sympy.core.function import Application, Derivative +from sympy.core.kind import BooleanKind, NumberKind +from sympy.core.numbers import Number +from sympy.core.operations import LatticeOp +from sympy.core.singleton import Singleton, S +from sympy.core.sorting import ordered +from sympy.core.sympify import _sympy_converter, _sympify, sympify +from sympy.utilities.iterables import sift, ibin +from sympy.utilities.misc import filldedent + + +def as_Boolean(e): + """Like ``bool``, return the Boolean value of an expression, e, + which can be any instance of :py:class:`~.Boolean` or ``bool``. + + Examples + ======== + + >>> from sympy import true, false, nan + >>> from sympy.logic.boolalg import as_Boolean + >>> from sympy.abc import x + >>> as_Boolean(0) is false + True + >>> as_Boolean(1) is true + True + >>> as_Boolean(x) + x + >>> as_Boolean(2) + Traceback (most recent call last): + ... + TypeError: expecting bool or Boolean, not `2`. + >>> as_Boolean(nan) + Traceback (most recent call last): + ... + TypeError: expecting bool or Boolean, not `nan`. + + """ + from sympy.core.symbol import Symbol + if e == True: + return true + if e == False: + return false + if isinstance(e, Symbol): + z = e.is_zero + if z is None: + return e + return false if z else true + if isinstance(e, Boolean): + return e + raise TypeError('expecting bool or Boolean, not `%s`.' % e) + + +@sympify_method_args +class Boolean(Basic): + """A Boolean object is an object for which logic operations make sense.""" + + __slots__ = () + + kind = BooleanKind + + @sympify_return([('other', 'Boolean')], NotImplemented) + def __and__(self, other): + return And(self, other) + + __rand__ = __and__ + + @sympify_return([('other', 'Boolean')], NotImplemented) + def __or__(self, other): + return Or(self, other) + + __ror__ = __or__ + + def __invert__(self): + """Overloading for ~""" + return Not(self) + + @sympify_return([('other', 'Boolean')], NotImplemented) + def __rshift__(self, other): + return Implies(self, other) + + @sympify_return([('other', 'Boolean')], NotImplemented) + def __lshift__(self, other): + return Implies(other, self) + + __rrshift__ = __lshift__ + __rlshift__ = __rshift__ + + @sympify_return([('other', 'Boolean')], NotImplemented) + def __xor__(self, other): + return Xor(self, other) + + __rxor__ = __xor__ + + def equals(self, other): + """ + Returns ``True`` if the given formulas have the same truth table. + For two formulas to be equal they must have the same literals. + + Examples + ======== + + >>> from sympy.abc import A, B, C + >>> from sympy import And, Or, Not + >>> (A >> B).equals(~B >> ~A) + True + >>> Not(And(A, B, C)).equals(And(Not(A), Not(B), Not(C))) + False + >>> Not(And(A, Not(A))).equals(Or(B, Not(B))) + False + + """ + from sympy.logic.inference import satisfiable + from sympy.core.relational import Relational + + if self.has(Relational) or other.has(Relational): + raise NotImplementedError('handling of relationals') + return self.atoms() == other.atoms() and \ + not satisfiable(Not(Equivalent(self, other))) + + def to_nnf(self, simplify=True): + # override where necessary + return self + + def as_set(self): + """ + Rewrites Boolean expression in terms of real sets. + + Examples + ======== + + >>> from sympy import Symbol, Eq, Or, And + >>> x = Symbol('x', real=True) + >>> Eq(x, 0).as_set() + {0} + >>> (x > 0).as_set() + Interval.open(0, oo) + >>> And(-2 < x, x < 2).as_set() + Interval.open(-2, 2) + >>> Or(x < -2, 2 < x).as_set() + Union(Interval.open(-oo, -2), Interval.open(2, oo)) + + """ + from sympy.calculus.util import periodicity + from sympy.core.relational import Relational + + free = self.free_symbols + if len(free) == 1: + x = free.pop() + if x.kind is NumberKind: + reps = {} + for r in self.atoms(Relational): + if periodicity(r, x) not in (0, None): + s = r._eval_as_set() + if s in (S.EmptySet, S.UniversalSet, S.Reals): + reps[r] = s.as_relational(x) + continue + raise NotImplementedError(filldedent(''' + as_set is not implemented for relationals + with periodic solutions + ''')) + new = self.subs(reps) + if new.func != self.func: + return new.as_set() # restart with new obj + else: + return new._eval_as_set() + + return self._eval_as_set() + else: + raise NotImplementedError("Sorry, as_set has not yet been" + " implemented for multivariate" + " expressions") + + @property + def binary_symbols(self): + from sympy.core.relational import Eq, Ne + return set().union(*[i.binary_symbols for i in self.args + if i.is_Boolean or i.is_Symbol + or isinstance(i, (Eq, Ne))]) + + def _eval_refine(self, assumptions): + from sympy.assumptions import ask + ret = ask(self, assumptions) + if ret is True: + return true + elif ret is False: + return false + return None + + +class BooleanAtom(Boolean): + """ + Base class of :py:class:`~.BooleanTrue` and :py:class:`~.BooleanFalse`. + """ + is_Boolean = True + is_Atom = True + _op_priority = 11 # higher than Expr + + def simplify(self, *a, **kw): + return self + + def expand(self, *a, **kw): + return self + + @property + def canonical(self): + return self + + def _noop(self, other=None): + raise TypeError('BooleanAtom not allowed in this context.') + + __add__ = _noop + __radd__ = _noop + __sub__ = _noop + __rsub__ = _noop + __mul__ = _noop + __rmul__ = _noop + __pow__ = _noop + __rpow__ = _noop + __truediv__ = _noop + __rtruediv__ = _noop + __mod__ = _noop + __rmod__ = _noop + _eval_power = _noop + + # /// drop when Py2 is no longer supported + def __lt__(self, other): + raise TypeError(filldedent(''' + A Boolean argument can only be used in + Eq and Ne; all other relationals expect + real expressions. + ''')) + + __le__ = __lt__ + __gt__ = __lt__ + __ge__ = __lt__ + # \\\ + + def _eval_simplify(self, **kwargs): + return self + + +class BooleanTrue(BooleanAtom, metaclass=Singleton): + """ + SymPy version of ``True``, a singleton that can be accessed via ``S.true``. + + This is the SymPy version of ``True``, for use in the logic module. The + primary advantage of using ``true`` instead of ``True`` is that shorthand Boolean + operations like ``~`` and ``>>`` will work as expected on this class, whereas with + True they act bitwise on 1. Functions in the logic module will return this + class when they evaluate to true. + + Notes + ===== + + There is liable to be some confusion as to when ``True`` should + be used and when ``S.true`` should be used in various contexts + throughout SymPy. An important thing to remember is that + ``sympify(True)`` returns ``S.true``. This means that for the most + part, you can just use ``True`` and it will automatically be converted + to ``S.true`` when necessary, similar to how you can generally use 1 + instead of ``S.One``. + + The rule of thumb is: + + "If the boolean in question can be replaced by an arbitrary symbolic + ``Boolean``, like ``Or(x, y)`` or ``x > 1``, use ``S.true``. + Otherwise, use ``True``" + + In other words, use ``S.true`` only on those contexts where the + boolean is being used as a symbolic representation of truth. + For example, if the object ends up in the ``.args`` of any expression, + then it must necessarily be ``S.true`` instead of ``True``, as + elements of ``.args`` must be ``Basic``. On the other hand, + ``==`` is not a symbolic operation in SymPy, since it always returns + ``True`` or ``False``, and does so in terms of structural equality + rather than mathematical, so it should return ``True``. The assumptions + system should use ``True`` and ``False``. Aside from not satisfying + the above rule of thumb, the assumptions system uses a three-valued logic + (``True``, ``False``, ``None``), whereas ``S.true`` and ``S.false`` + represent a two-valued logic. When in doubt, use ``True``. + + "``S.true == True is True``." + + While "``S.true is True``" is ``False``, "``S.true == True``" + is ``True``, so if there is any doubt over whether a function or + expression will return ``S.true`` or ``True``, just use ``==`` + instead of ``is`` to do the comparison, and it will work in either + case. Finally, for boolean flags, it's better to just use ``if x`` + instead of ``if x is True``. To quote PEP 8: + + Do not compare boolean values to ``True`` or ``False`` + using ``==``. + + * Yes: ``if greeting:`` + * No: ``if greeting == True:`` + * Worse: ``if greeting is True:`` + + Examples + ======== + + >>> from sympy import sympify, true, false, Or + >>> sympify(True) + True + >>> _ is True, _ is true + (False, True) + + >>> Or(true, false) + True + >>> _ is true + True + + Python operators give a boolean result for true but a + bitwise result for True + + >>> ~true, ~True + (False, -2) + >>> true >> true, True >> True + (True, 0) + + Python operators give a boolean result for true but a + bitwise result for True + + >>> ~true, ~True + (False, -2) + >>> true >> true, True >> True + (True, 0) + + See Also + ======== + + sympy.logic.boolalg.BooleanFalse + + """ + def __bool__(self): + return True + + def __hash__(self): + return hash(True) + + def __eq__(self, other): + if other is True: + return True + if other is False: + return False + return super().__eq__(other) + + @property + def negated(self): + return false + + def as_set(self): + """ + Rewrite logic operators and relationals in terms of real sets. + + Examples + ======== + + >>> from sympy import true + >>> true.as_set() + UniversalSet + + """ + return S.UniversalSet + + +class BooleanFalse(BooleanAtom, metaclass=Singleton): + """ + SymPy version of ``False``, a singleton that can be accessed via ``S.false``. + + This is the SymPy version of ``False``, for use in the logic module. The + primary advantage of using ``false`` instead of ``False`` is that shorthand + Boolean operations like ``~`` and ``>>`` will work as expected on this class, + whereas with ``False`` they act bitwise on 0. Functions in the logic module + will return this class when they evaluate to false. + + Notes + ====== + + See the notes section in :py:class:`sympy.logic.boolalg.BooleanTrue` + + Examples + ======== + + >>> from sympy import sympify, true, false, Or + >>> sympify(False) + False + >>> _ is False, _ is false + (False, True) + + >>> Or(true, false) + True + >>> _ is true + True + + Python operators give a boolean result for false but a + bitwise result for False + + >>> ~false, ~False + (True, -1) + >>> false >> false, False >> False + (True, 0) + + See Also + ======== + + sympy.logic.boolalg.BooleanTrue + + """ + def __bool__(self): + return False + + def __hash__(self): + return hash(False) + + def __eq__(self, other): + if other is True: + return False + if other is False: + return True + return super().__eq__(other) + + @property + def negated(self): + return true + + def as_set(self): + """ + Rewrite logic operators and relationals in terms of real sets. + + Examples + ======== + + >>> from sympy import false + >>> false.as_set() + EmptySet + """ + return S.EmptySet + + +true = BooleanTrue() +false = BooleanFalse() +# We want S.true and S.false to work, rather than S.BooleanTrue and +# S.BooleanFalse, but making the class and instance names the same causes some +# major issues (like the inability to import the class directly from this +# file). +S.true = true +S.false = false + +_sympy_converter[bool] = lambda x: true if x else false + + +class BooleanFunction(Application, Boolean): + """Boolean function is a function that lives in a boolean space + It is used as base class for :py:class:`~.And`, :py:class:`~.Or`, + :py:class:`~.Not`, etc. + """ + is_Boolean = True + + def _eval_simplify(self, **kwargs): + rv = simplify_univariate(self) + if not isinstance(rv, BooleanFunction): + return rv.simplify(**kwargs) + rv = rv.func(*[a.simplify(**kwargs) for a in rv.args]) + return simplify_logic(rv) + + def simplify(self, **kwargs): + from sympy.simplify.simplify import simplify + return simplify(self, **kwargs) + + def __lt__(self, other): + raise TypeError(filldedent(''' + A Boolean argument can only be used in + Eq and Ne; all other relationals expect + real expressions. + ''')) + __le__ = __lt__ + __ge__ = __lt__ + __gt__ = __lt__ + + @classmethod + def binary_check_and_simplify(self, *args): + from sympy.core.relational import Relational, Eq, Ne + args = [as_Boolean(i) for i in args] + bin_syms = set().union(*[i.binary_symbols for i in args]) + rel = set().union(*[i.atoms(Relational) for i in args]) + reps = {} + for x in bin_syms: + for r in rel: + if x in bin_syms and x in r.free_symbols: + if isinstance(r, (Eq, Ne)): + if not ( + true in r.args or + false in r.args): + reps[r] = false + else: + raise TypeError(filldedent(''' + Incompatible use of binary symbol `%s` as a + real variable in `%s` + ''' % (x, r))) + return [i.subs(reps) for i in args] + + def to_nnf(self, simplify=True): + return self._to_nnf(*self.args, simplify=simplify) + + def to_anf(self, deep=True): + return self._to_anf(*self.args, deep=deep) + + @classmethod + def _to_nnf(cls, *args, **kwargs): + simplify = kwargs.get('simplify', True) + argset = set() + for arg in args: + if not is_literal(arg): + arg = arg.to_nnf(simplify) + if simplify: + if isinstance(arg, cls): + arg = arg.args + else: + arg = (arg,) + for a in arg: + if Not(a) in argset: + return cls.zero + argset.add(a) + else: + argset.add(arg) + return cls(*argset) + + @classmethod + def _to_anf(cls, *args, **kwargs): + deep = kwargs.get('deep', True) + argset = set() + for arg in args: + if deep: + if not is_literal(arg) or isinstance(arg, Not): + arg = arg.to_anf(deep=deep) + argset.add(arg) + else: + argset.add(arg) + return cls(*argset, remove_true=False) + + # the diff method below is copied from Expr class + def diff(self, *symbols, **assumptions): + assumptions.setdefault("evaluate", True) + return Derivative(self, *symbols, **assumptions) + + def _eval_derivative(self, x): + if x in self.binary_symbols: + from sympy.core.relational import Eq + from sympy.functions.elementary.piecewise import Piecewise + return Piecewise( + (0, Eq(self.subs(x, 0), self.subs(x, 1))), + (1, True)) + elif x in self.free_symbols: + # not implemented, see https://www.encyclopediaofmath.org/ + # index.php/Boolean_differential_calculus + pass + else: + return S.Zero + + +class And(LatticeOp, BooleanFunction): + """ + Logical AND function. + + It evaluates its arguments in order, returning false immediately + when an argument is false and true if they are all true. + + Examples + ======== + + >>> from sympy.abc import x, y + >>> from sympy import And + >>> x & y + x & y + + Notes + ===== + + The ``&`` operator is provided as a convenience, but note that its use + here is different from its normal use in Python, which is bitwise + and. Hence, ``And(a, b)`` and ``a & b`` will produce different results if + ``a`` and ``b`` are integers. + + >>> And(x, y).subs(x, 1) + y + + """ + zero = false + identity = true + + nargs = None + + @classmethod + def _new_args_filter(cls, args): + args = BooleanFunction.binary_check_and_simplify(*args) + args = LatticeOp._new_args_filter(args, And) + newargs = [] + rel = set() + for x in ordered(args): + if x.is_Relational: + c = x.canonical + if c in rel: + continue + elif c.negated.canonical in rel: + return [false] + else: + rel.add(c) + newargs.append(x) + return newargs + + def _eval_subs(self, old, new): + args = [] + bad = None + for i in self.args: + try: + i = i.subs(old, new) + except TypeError: + # store TypeError + if bad is None: + bad = i + continue + if i == False: + return false + elif i != True: + args.append(i) + if bad is not None: + # let it raise + bad.subs(old, new) + # If old is And, replace the parts of the arguments with new if all + # are there + if isinstance(old, And): + old_set = set(old.args) + if old_set.issubset(args): + args = set(args) - old_set + args.add(new) + + return self.func(*args) + + def _eval_simplify(self, **kwargs): + from sympy.core.relational import Equality, Relational + from sympy.solvers.solveset import linear_coeffs + # standard simplify + rv = super()._eval_simplify(**kwargs) + if not isinstance(rv, And): + return rv + + # simplify args that are equalities involving + # symbols so x == 0 & x == y -> x==0 & y == 0 + Rel, nonRel = sift(rv.args, lambda i: isinstance(i, Relational), + binary=True) + if not Rel: + return rv + eqs, other = sift(Rel, lambda i: isinstance(i, Equality), binary=True) + + measure = kwargs['measure'] + if eqs: + ratio = kwargs['ratio'] + reps = {} + sifted = {} + # group by length of free symbols + sifted = sift(ordered([ + (i.free_symbols, i) for i in eqs]), + lambda x: len(x[0])) + eqs = [] + nonlineqs = [] + while 1 in sifted: + for free, e in sifted.pop(1): + x = free.pop() + if (e.lhs != x or x in e.rhs.free_symbols) and x not in reps: + try: + m, b = linear_coeffs( + e.rewrite(Add, evaluate=False), x) + enew = e.func(x, -b/m) + if measure(enew) <= ratio*measure(e): + e = enew + else: + eqs.append(e) + continue + except ValueError: + pass + if x in reps: + eqs.append(e.subs(x, reps[x])) + elif e.lhs == x and x not in e.rhs.free_symbols: + reps[x] = e.rhs + eqs.append(e) + else: + # x is not yet identified, but may be later + nonlineqs.append(e) + resifted = defaultdict(list) + for k in sifted: + for f, e in sifted[k]: + e = e.xreplace(reps) + f = e.free_symbols + resifted[len(f)].append((f, e)) + sifted = resifted + for k in sifted: + eqs.extend([e for f, e in sifted[k]]) + nonlineqs = [ei.subs(reps) for ei in nonlineqs] + other = [ei.subs(reps) for ei in other] + rv = rv.func(*([i.canonical for i in (eqs + nonlineqs + other)] + nonRel)) + patterns = _simplify_patterns_and() + threeterm_patterns = _simplify_patterns_and3() + return _apply_patternbased_simplification(rv, patterns, + measure, false, + threeterm_patterns=threeterm_patterns) + + def _eval_as_set(self): + from sympy.sets.sets import Intersection + return Intersection(*[arg.as_set() for arg in self.args]) + + def _eval_rewrite_as_Nor(self, *args, **kwargs): + return Nor(*[Not(arg) for arg in self.args]) + + def to_anf(self, deep=True): + if deep: + result = And._to_anf(*self.args, deep=deep) + return distribute_xor_over_and(result) + return self + + +class Or(LatticeOp, BooleanFunction): + """ + Logical OR function + + It evaluates its arguments in order, returning true immediately + when an argument is true, and false if they are all false. + + Examples + ======== + + >>> from sympy.abc import x, y + >>> from sympy import Or + >>> x | y + x | y + + Notes + ===== + + The ``|`` operator is provided as a convenience, but note that its use + here is different from its normal use in Python, which is bitwise + or. Hence, ``Or(a, b)`` and ``a | b`` will return different things if + ``a`` and ``b`` are integers. + + >>> Or(x, y).subs(x, 0) + y + + """ + zero = true + identity = false + + @classmethod + def _new_args_filter(cls, args): + newargs = [] + rel = [] + args = BooleanFunction.binary_check_and_simplify(*args) + for x in args: + if x.is_Relational: + c = x.canonical + if c in rel: + continue + nc = c.negated.canonical + if any(r == nc for r in rel): + return [true] + rel.append(c) + newargs.append(x) + return LatticeOp._new_args_filter(newargs, Or) + + def _eval_subs(self, old, new): + args = [] + bad = None + for i in self.args: + try: + i = i.subs(old, new) + except TypeError: + # store TypeError + if bad is None: + bad = i + continue + if i == True: + return true + elif i != False: + args.append(i) + if bad is not None: + # let it raise + bad.subs(old, new) + # If old is Or, replace the parts of the arguments with new if all + # are there + if isinstance(old, Or): + old_set = set(old.args) + if old_set.issubset(args): + args = set(args) - old_set + args.add(new) + + return self.func(*args) + + def _eval_as_set(self): + from sympy.sets.sets import Union + return Union(*[arg.as_set() for arg in self.args]) + + def _eval_rewrite_as_Nand(self, *args, **kwargs): + return Nand(*[Not(arg) for arg in self.args]) + + def _eval_simplify(self, **kwargs): + from sympy.core.relational import Le, Ge, Eq + lege = self.atoms(Le, Ge) + if lege: + reps = {i: self.func( + Eq(i.lhs, i.rhs), i.strict) for i in lege} + return self.xreplace(reps)._eval_simplify(**kwargs) + # standard simplify + rv = super()._eval_simplify(**kwargs) + if not isinstance(rv, Or): + return rv + patterns = _simplify_patterns_or() + return _apply_patternbased_simplification(rv, patterns, + kwargs['measure'], true) + + def to_anf(self, deep=True): + args = range(1, len(self.args) + 1) + args = (combinations(self.args, j) for j in args) + args = chain.from_iterable(args) # powerset + args = (And(*arg) for arg in args) + args = (to_anf(x, deep=deep) if deep else x for x in args) + return Xor(*list(args), remove_true=False) + + +class Not(BooleanFunction): + """ + Logical Not function (negation) + + + Returns ``true`` if the statement is ``false`` or ``False``. + Returns ``false`` if the statement is ``true`` or ``True``. + + Examples + ======== + + >>> from sympy import Not, And, Or + >>> from sympy.abc import x, A, B + >>> Not(True) + False + >>> Not(False) + True + >>> Not(And(True, False)) + True + >>> Not(Or(True, False)) + False + >>> Not(And(And(True, x), Or(x, False))) + ~x + >>> ~x + ~x + >>> Not(And(Or(A, B), Or(~A, ~B))) + ~((A | B) & (~A | ~B)) + + Notes + ===== + + - The ``~`` operator is provided as a convenience, but note that its use + here is different from its normal use in Python, which is bitwise + not. In particular, ``~a`` and ``Not(a)`` will be different if ``a`` is + an integer. Furthermore, since bools in Python subclass from ``int``, + ``~True`` is the same as ``~1`` which is ``-2``, which has a boolean + value of True. To avoid this issue, use the SymPy boolean types + ``true`` and ``false``. + + >>> from sympy import true + >>> ~True + -2 + >>> ~true + False + + """ + + is_Not = True + + @classmethod + def eval(cls, arg): + if isinstance(arg, Number) or arg in (True, False): + return false if arg else true + if arg.is_Not: + return arg.args[0] + # Simplify Relational objects. + if arg.is_Relational: + return arg.negated + + def _eval_as_set(self): + """ + Rewrite logic operators and relationals in terms of real sets. + + Examples + ======== + + >>> from sympy import Not, Symbol + >>> x = Symbol('x') + >>> Not(x > 0).as_set() + Interval(-oo, 0) + """ + return self.args[0].as_set().complement(S.Reals) + + def to_nnf(self, simplify=True): + if is_literal(self): + return self + + expr = self.args[0] + + func, args = expr.func, expr.args + + if func == And: + return Or._to_nnf(*[Not(arg) for arg in args], simplify=simplify) + + if func == Or: + return And._to_nnf(*[Not(arg) for arg in args], simplify=simplify) + + if func == Implies: + a, b = args + return And._to_nnf(a, Not(b), simplify=simplify) + + if func == Equivalent: + return And._to_nnf(Or(*args), Or(*[Not(arg) for arg in args]), + simplify=simplify) + + if func == Xor: + result = [] + for i in range(1, len(args)+1, 2): + for neg in combinations(args, i): + clause = [Not(s) if s in neg else s for s in args] + result.append(Or(*clause)) + return And._to_nnf(*result, simplify=simplify) + + if func == ITE: + a, b, c = args + return And._to_nnf(Or(a, Not(c)), Or(Not(a), Not(b)), simplify=simplify) + + raise ValueError("Illegal operator %s in expression" % func) + + def to_anf(self, deep=True): + return Xor._to_anf(true, self.args[0], deep=deep) + + +class Xor(BooleanFunction): + """ + Logical XOR (exclusive OR) function. + + + Returns True if an odd number of the arguments are True and the rest are + False. + + Returns False if an even number of the arguments are True and the rest are + False. + + Examples + ======== + + >>> from sympy.logic.boolalg import Xor + >>> from sympy import symbols + >>> x, y = symbols('x y') + >>> Xor(True, False) + True + >>> Xor(True, True) + False + >>> Xor(True, False, True, True, False) + True + >>> Xor(True, False, True, False) + False + >>> x ^ y + x ^ y + + Notes + ===== + + The ``^`` operator is provided as a convenience, but note that its use + here is different from its normal use in Python, which is bitwise xor. In + particular, ``a ^ b`` and ``Xor(a, b)`` will be different if ``a`` and + ``b`` are integers. + + >>> Xor(x, y).subs(y, 0) + x + + """ + def __new__(cls, *args, remove_true=True, **kwargs): + argset = set() + obj = super().__new__(cls, *args, **kwargs) + for arg in obj._args: + if isinstance(arg, Number) or arg in (True, False): + if arg: + arg = true + else: + continue + if isinstance(arg, Xor): + for a in arg.args: + argset.remove(a) if a in argset else argset.add(a) + elif arg in argset: + argset.remove(arg) + else: + argset.add(arg) + rel = [(r, r.canonical, r.negated.canonical) + for r in argset if r.is_Relational] + odd = False # is number of complimentary pairs odd? start 0 -> False + remove = [] + for i, (r, c, nc) in enumerate(rel): + for j in range(i + 1, len(rel)): + rj, cj = rel[j][:2] + if cj == nc: + odd = ~odd + break + elif cj == c: + break + else: + continue + remove.append((r, rj)) + if odd: + argset.remove(true) if true in argset else argset.add(true) + for a, b in remove: + argset.remove(a) + argset.remove(b) + if len(argset) == 0: + return false + elif len(argset) == 1: + return argset.pop() + elif True in argset and remove_true: + argset.remove(True) + return Not(Xor(*argset)) + else: + obj._args = tuple(ordered(argset)) + obj._argset = frozenset(argset) + return obj + + # XXX: This should be cached on the object rather than using cacheit + # Maybe it can be computed in __new__? + @property # type: ignore + @cacheit + def args(self): + return tuple(ordered(self._argset)) + + def to_nnf(self, simplify=True): + args = [] + for i in range(0, len(self.args)+1, 2): + for neg in combinations(self.args, i): + clause = [Not(s) if s in neg else s for s in self.args] + args.append(Or(*clause)) + return And._to_nnf(*args, simplify=simplify) + + def _eval_rewrite_as_Or(self, *args, **kwargs): + a = self.args + return Or(*[_convert_to_varsSOP(x, self.args) + for x in _get_odd_parity_terms(len(a))]) + + def _eval_rewrite_as_And(self, *args, **kwargs): + a = self.args + return And(*[_convert_to_varsPOS(x, self.args) + for x in _get_even_parity_terms(len(a))]) + + def _eval_simplify(self, **kwargs): + # as standard simplify uses simplify_logic which writes things as + # And and Or, we only simplify the partial expressions before using + # patterns + rv = self.func(*[a.simplify(**kwargs) for a in self.args]) + if not isinstance(rv, Xor): # This shouldn't really happen here + return rv + patterns = _simplify_patterns_xor() + return _apply_patternbased_simplification(rv, patterns, + kwargs['measure'], None) + + def _eval_subs(self, old, new): + # If old is Xor, replace the parts of the arguments with new if all + # are there + if isinstance(old, Xor): + old_set = set(old.args) + if old_set.issubset(self.args): + args = set(self.args) - old_set + args.add(new) + return self.func(*args) + + +class Nand(BooleanFunction): + """ + Logical NAND function. + + It evaluates its arguments in order, giving True immediately if any + of them are False, and False if they are all True. + + Returns True if any of the arguments are False + Returns False if all arguments are True + + Examples + ======== + + >>> from sympy.logic.boolalg import Nand + >>> from sympy import symbols + >>> x, y = symbols('x y') + >>> Nand(False, True) + True + >>> Nand(True, True) + False + >>> Nand(x, y) + ~(x & y) + + """ + @classmethod + def eval(cls, *args): + return Not(And(*args)) + + +class Nor(BooleanFunction): + """ + Logical NOR function. + + It evaluates its arguments in order, giving False immediately if any + of them are True, and True if they are all False. + + Returns False if any argument is True + Returns True if all arguments are False + + Examples + ======== + + >>> from sympy.logic.boolalg import Nor + >>> from sympy import symbols + >>> x, y = symbols('x y') + + >>> Nor(True, False) + False + >>> Nor(True, True) + False + >>> Nor(False, True) + False + >>> Nor(False, False) + True + >>> Nor(x, y) + ~(x | y) + + """ + @classmethod + def eval(cls, *args): + return Not(Or(*args)) + + +class Xnor(BooleanFunction): + """ + Logical XNOR function. + + Returns False if an odd number of the arguments are True and the rest are + False. + + Returns True if an even number of the arguments are True and the rest are + False. + + Examples + ======== + + >>> from sympy.logic.boolalg import Xnor + >>> from sympy import symbols + >>> x, y = symbols('x y') + >>> Xnor(True, False) + False + >>> Xnor(True, True) + True + >>> Xnor(True, False, True, True, False) + False + >>> Xnor(True, False, True, False) + True + + """ + @classmethod + def eval(cls, *args): + return Not(Xor(*args)) + + +class Implies(BooleanFunction): + r""" + Logical implication. + + A implies B is equivalent to if A then B. Mathematically, it is written + as `A \Rightarrow B` and is equivalent to `\neg A \vee B` or ``~A | B``. + + Accepts two Boolean arguments; A and B. + Returns False if A is True and B is False + Returns True otherwise. + + Examples + ======== + + >>> from sympy.logic.boolalg import Implies + >>> from sympy import symbols + >>> x, y = symbols('x y') + + >>> Implies(True, False) + False + >>> Implies(False, False) + True + >>> Implies(True, True) + True + >>> Implies(False, True) + True + >>> x >> y + Implies(x, y) + >>> y << x + Implies(x, y) + + Notes + ===== + + The ``>>`` and ``<<`` operators are provided as a convenience, but note + that their use here is different from their normal use in Python, which is + bit shifts. Hence, ``Implies(a, b)`` and ``a >> b`` will return different + things if ``a`` and ``b`` are integers. In particular, since Python + considers ``True`` and ``False`` to be integers, ``True >> True`` will be + the same as ``1 >> 1``, i.e., 0, which has a truth value of False. To + avoid this issue, use the SymPy objects ``true`` and ``false``. + + >>> from sympy import true, false + >>> True >> False + 1 + >>> true >> false + False + + """ + @classmethod + def eval(cls, *args): + try: + newargs = [] + for x in args: + if isinstance(x, Number) or x in (0, 1): + newargs.append(bool(x)) + else: + newargs.append(x) + A, B = newargs + except ValueError: + raise ValueError( + "%d operand(s) used for an Implies " + "(pairs are required): %s" % (len(args), str(args))) + if A in (True, False) or B in (True, False): + return Or(Not(A), B) + elif A == B: + return true + elif A.is_Relational and B.is_Relational: + if A.canonical == B.canonical: + return true + if A.negated.canonical == B.canonical: + return B + else: + return Basic.__new__(cls, *args) + + def to_nnf(self, simplify=True): + a, b = self.args + return Or._to_nnf(Not(a), b, simplify=simplify) + + def to_anf(self, deep=True): + a, b = self.args + return Xor._to_anf(true, a, And(a, b), deep=deep) + + +class Equivalent(BooleanFunction): + """ + Equivalence relation. + + ``Equivalent(A, B)`` is True iff A and B are both True or both False. + + Returns True if all of the arguments are logically equivalent. + Returns False otherwise. + + For two arguments, this is equivalent to :py:class:`~.Xnor`. + + Examples + ======== + + >>> from sympy.logic.boolalg import Equivalent, And + >>> from sympy.abc import x + >>> Equivalent(False, False, False) + True + >>> Equivalent(True, False, False) + False + >>> Equivalent(x, And(x, True)) + True + + """ + def __new__(cls, *args, **options): + from sympy.core.relational import Relational + args = [_sympify(arg) for arg in args] + + argset = set(args) + for x in args: + if isinstance(x, Number) or x in [True, False]: # Includes 0, 1 + argset.discard(x) + argset.add(bool(x)) + rel = [] + for r in argset: + if isinstance(r, Relational): + rel.append((r, r.canonical, r.negated.canonical)) + remove = [] + for i, (r, c, nc) in enumerate(rel): + for j in range(i + 1, len(rel)): + rj, cj = rel[j][:2] + if cj == nc: + return false + elif cj == c: + remove.append((r, rj)) + break + for a, b in remove: + argset.remove(a) + argset.remove(b) + argset.add(True) + if len(argset) <= 1: + return true + if True in argset: + argset.discard(True) + return And(*argset) + if False in argset: + argset.discard(False) + return And(*[Not(arg) for arg in argset]) + _args = frozenset(argset) + obj = super().__new__(cls, _args) + obj._argset = _args + return obj + + # XXX: This should be cached on the object rather than using cacheit + # Maybe it can be computed in __new__? + @property # type: ignore + @cacheit + def args(self): + return tuple(ordered(self._argset)) + + def to_nnf(self, simplify=True): + args = [] + for a, b in zip(self.args, self.args[1:]): + args.append(Or(Not(a), b)) + args.append(Or(Not(self.args[-1]), self.args[0])) + return And._to_nnf(*args, simplify=simplify) + + def to_anf(self, deep=True): + a = And(*self.args) + b = And(*[to_anf(Not(arg), deep=False) for arg in self.args]) + b = distribute_xor_over_and(b) + return Xor._to_anf(a, b, deep=deep) + + +class ITE(BooleanFunction): + """ + If-then-else clause. + + ``ITE(A, B, C)`` evaluates and returns the result of B if A is true + else it returns the result of C. All args must be Booleans. + + From a logic gate perspective, ITE corresponds to a 2-to-1 multiplexer, + where A is the select signal. + + Examples + ======== + + >>> from sympy.logic.boolalg import ITE, And, Xor, Or + >>> from sympy.abc import x, y, z + >>> ITE(True, False, True) + False + >>> ITE(Or(True, False), And(True, True), Xor(True, True)) + True + >>> ITE(x, y, z) + ITE(x, y, z) + >>> ITE(True, x, y) + x + >>> ITE(False, x, y) + y + >>> ITE(x, y, y) + y + + Trying to use non-Boolean args will generate a TypeError: + + >>> ITE(True, [], ()) + Traceback (most recent call last): + ... + TypeError: expecting bool, Boolean or ITE, not `[]` + + """ + def __new__(cls, *args, **kwargs): + from sympy.core.relational import Eq, Ne + if len(args) != 3: + raise ValueError('expecting exactly 3 args') + a, b, c = args + # check use of binary symbols + if isinstance(a, (Eq, Ne)): + # in this context, we can evaluate the Eq/Ne + # if one arg is a binary symbol and the other + # is true/false + b, c = map(as_Boolean, (b, c)) + bin_syms = set().union(*[i.binary_symbols for i in (b, c)]) + if len(set(a.args) - bin_syms) == 1: + # one arg is a binary_symbols + _a = a + if a.lhs is true: + a = a.rhs + elif a.rhs is true: + a = a.lhs + elif a.lhs is false: + a = Not(a.rhs) + elif a.rhs is false: + a = Not(a.lhs) + else: + # binary can only equal True or False + a = false + if isinstance(_a, Ne): + a = Not(a) + else: + a, b, c = BooleanFunction.binary_check_and_simplify( + a, b, c) + rv = None + if kwargs.get('evaluate', True): + rv = cls.eval(a, b, c) + if rv is None: + rv = BooleanFunction.__new__(cls, a, b, c, evaluate=False) + return rv + + @classmethod + def eval(cls, *args): + from sympy.core.relational import Eq, Ne + # do the args give a singular result? + a, b, c = args + if isinstance(a, (Ne, Eq)): + _a = a + if true in a.args: + a = a.lhs if a.rhs is true else a.rhs + elif false in a.args: + a = Not(a.lhs) if a.rhs is false else Not(a.rhs) + else: + _a = None + if _a is not None and isinstance(_a, Ne): + a = Not(a) + if a is true: + return b + if a is false: + return c + if b == c: + return b + else: + # or maybe the results allow the answer to be expressed + # in terms of the condition + if b is true and c is false: + return a + if b is false and c is true: + return Not(a) + if [a, b, c] != args: + return cls(a, b, c, evaluate=False) + + def to_nnf(self, simplify=True): + a, b, c = self.args + return And._to_nnf(Or(Not(a), b), Or(a, c), simplify=simplify) + + def _eval_as_set(self): + return self.to_nnf().as_set() + + def _eval_rewrite_as_Piecewise(self, *args, **kwargs): + from sympy.functions.elementary.piecewise import Piecewise + return Piecewise((args[1], args[0]), (args[2], True)) + + +class Exclusive(BooleanFunction): + """ + True if only one or no argument is true. + + ``Exclusive(A, B, C)`` is equivalent to ``~(A & B) & ~(A & C) & ~(B & C)``. + + For two arguments, this is equivalent to :py:class:`~.Xor`. + + Examples + ======== + + >>> from sympy.logic.boolalg import Exclusive + >>> Exclusive(False, False, False) + True + >>> Exclusive(False, True, False) + True + >>> Exclusive(False, True, True) + False + + """ + @classmethod + def eval(cls, *args): + and_args = [] + for a, b in combinations(args, 2): + and_args.append(Not(And(a, b))) + return And(*and_args) + + +# end class definitions. Some useful methods + + +def conjuncts(expr): + """Return a list of the conjuncts in ``expr``. + + Examples + ======== + + >>> from sympy.logic.boolalg import conjuncts + >>> from sympy.abc import A, B + >>> conjuncts(A & B) + frozenset({A, B}) + >>> conjuncts(A | B) + frozenset({A | B}) + + """ + return And.make_args(expr) + + +def disjuncts(expr): + """Return a list of the disjuncts in ``expr``. + + Examples + ======== + + >>> from sympy.logic.boolalg import disjuncts + >>> from sympy.abc import A, B + >>> disjuncts(A | B) + frozenset({A, B}) + >>> disjuncts(A & B) + frozenset({A & B}) + + """ + return Or.make_args(expr) + + +def distribute_and_over_or(expr): + """ + Given a sentence ``expr`` consisting of conjunctions and disjunctions + of literals, return an equivalent sentence in CNF. + + Examples + ======== + + >>> from sympy.logic.boolalg import distribute_and_over_or, And, Or, Not + >>> from sympy.abc import A, B, C + >>> distribute_and_over_or(Or(A, And(Not(B), Not(C)))) + (A | ~B) & (A | ~C) + + """ + return _distribute((expr, And, Or)) + + +def distribute_or_over_and(expr): + """ + Given a sentence ``expr`` consisting of conjunctions and disjunctions + of literals, return an equivalent sentence in DNF. + + Note that the output is NOT simplified. + + Examples + ======== + + >>> from sympy.logic.boolalg import distribute_or_over_and, And, Or, Not + >>> from sympy.abc import A, B, C + >>> distribute_or_over_and(And(Or(Not(A), B), C)) + (B & C) | (C & ~A) + + """ + return _distribute((expr, Or, And)) + + +def distribute_xor_over_and(expr): + """ + Given a sentence ``expr`` consisting of conjunction and + exclusive disjunctions of literals, return an + equivalent exclusive disjunction. + + Note that the output is NOT simplified. + + Examples + ======== + + >>> from sympy.logic.boolalg import distribute_xor_over_and, And, Xor, Not + >>> from sympy.abc import A, B, C + >>> distribute_xor_over_and(And(Xor(Not(A), B), C)) + (B & C) ^ (C & ~A) + """ + return _distribute((expr, Xor, And)) + + +def _distribute(info): + """ + Distributes ``info[1]`` over ``info[2]`` with respect to ``info[0]``. + """ + if isinstance(info[0], info[2]): + for arg in info[0].args: + if isinstance(arg, info[1]): + conj = arg + break + else: + return info[0] + rest = info[2](*[a for a in info[0].args if a is not conj]) + return info[1](*list(map(_distribute, + [(info[2](c, rest), info[1], info[2]) + for c in conj.args])), remove_true=False) + elif isinstance(info[0], info[1]): + return info[1](*list(map(_distribute, + [(x, info[1], info[2]) + for x in info[0].args])), + remove_true=False) + else: + return info[0] + + +def to_anf(expr, deep=True): + r""" + Converts expr to Algebraic Normal Form (ANF). + + ANF is a canonical normal form, which means that two + equivalent formulas will convert to the same ANF. + + A logical expression is in ANF if it has the form + + .. math:: 1 \oplus a \oplus b \oplus ab \oplus abc + + i.e. it can be: + - purely true, + - purely false, + - conjunction of variables, + - exclusive disjunction. + + The exclusive disjunction can only contain true, variables + or conjunction of variables. No negations are permitted. + + If ``deep`` is ``False``, arguments of the boolean + expression are considered variables, i.e. only the + top-level expression is converted to ANF. + + Examples + ======== + >>> from sympy.logic.boolalg import And, Or, Not, Implies, Equivalent + >>> from sympy.logic.boolalg import to_anf + >>> from sympy.abc import A, B, C + >>> to_anf(Not(A)) + A ^ True + >>> to_anf(And(Or(A, B), Not(C))) + A ^ B ^ (A & B) ^ (A & C) ^ (B & C) ^ (A & B & C) + >>> to_anf(Implies(Not(A), Equivalent(B, C)), deep=False) + True ^ ~A ^ (~A & (Equivalent(B, C))) + + """ + expr = sympify(expr) + + if is_anf(expr): + return expr + return expr.to_anf(deep=deep) + + +def to_nnf(expr, simplify=True): + """ + Converts ``expr`` to Negation Normal Form (NNF). + + A logical expression is in NNF if it + contains only :py:class:`~.And`, :py:class:`~.Or` and :py:class:`~.Not`, + and :py:class:`~.Not` is applied only to literals. + If ``simplify`` is ``True``, the result contains no redundant clauses. + + Examples + ======== + + >>> from sympy.abc import A, B, C, D + >>> from sympy.logic.boolalg import Not, Equivalent, to_nnf + >>> to_nnf(Not((~A & ~B) | (C & D))) + (A | B) & (~C | ~D) + >>> to_nnf(Equivalent(A >> B, B >> A)) + (A | ~B | (A & ~B)) & (B | ~A | (B & ~A)) + + """ + if is_nnf(expr, simplify): + return expr + return expr.to_nnf(simplify) + + +def to_cnf(expr, simplify=False, force=False): + """ + Convert a propositional logical sentence ``expr`` to conjunctive normal + form: ``((A | ~B | ...) & (B | C | ...) & ...)``. + If ``simplify`` is ``True``, ``expr`` is evaluated to its simplest CNF + form using the Quine-McCluskey algorithm; this may take a long + time. If there are more than 8 variables the ``force`` flag must be set + to ``True`` to simplify (default is ``False``). + + Examples + ======== + + >>> from sympy.logic.boolalg import to_cnf + >>> from sympy.abc import A, B, D + >>> to_cnf(~(A | B) | D) + (D | ~A) & (D | ~B) + >>> to_cnf((A | B) & (A | ~A), True) + A | B + + """ + expr = sympify(expr) + if not isinstance(expr, BooleanFunction): + return expr + + if simplify: + if not force and len(_find_predicates(expr)) > 8: + raise ValueError(filldedent(''' + To simplify a logical expression with more + than 8 variables may take a long time and requires + the use of `force=True`.''')) + return simplify_logic(expr, 'cnf', True, force=force) + + # Don't convert unless we have to + if is_cnf(expr): + return expr + + expr = eliminate_implications(expr) + res = distribute_and_over_or(expr) + + return res + + +def to_dnf(expr, simplify=False, force=False): + """ + Convert a propositional logical sentence ``expr`` to disjunctive normal + form: ``((A & ~B & ...) | (B & C & ...) | ...)``. + If ``simplify`` is ``True``, ``expr`` is evaluated to its simplest DNF form using + the Quine-McCluskey algorithm; this may take a long + time. If there are more than 8 variables, the ``force`` flag must be set to + ``True`` to simplify (default is ``False``). + + Examples + ======== + + >>> from sympy.logic.boolalg import to_dnf + >>> from sympy.abc import A, B, C + >>> to_dnf(B & (A | C)) + (A & B) | (B & C) + >>> to_dnf((A & B) | (A & ~B) | (B & C) | (~B & C), True) + A | C + + """ + expr = sympify(expr) + if not isinstance(expr, BooleanFunction): + return expr + + if simplify: + if not force and len(_find_predicates(expr)) > 8: + raise ValueError(filldedent(''' + To simplify a logical expression with more + than 8 variables may take a long time and requires + the use of `force=True`.''')) + return simplify_logic(expr, 'dnf', True, force=force) + + # Don't convert unless we have to + if is_dnf(expr): + return expr + + expr = eliminate_implications(expr) + return distribute_or_over_and(expr) + + +def is_anf(expr): + r""" + Checks if ``expr`` is in Algebraic Normal Form (ANF). + + A logical expression is in ANF if it has the form + + .. math:: 1 \oplus a \oplus b \oplus ab \oplus abc + + i.e. it is purely true, purely false, conjunction of + variables or exclusive disjunction. The exclusive + disjunction can only contain true, variables or + conjunction of variables. No negations are permitted. + + Examples + ======== + + >>> from sympy.logic.boolalg import And, Not, Xor, true, is_anf + >>> from sympy.abc import A, B, C + >>> is_anf(true) + True + >>> is_anf(A) + True + >>> is_anf(And(A, B, C)) + True + >>> is_anf(Xor(A, Not(B))) + False + + """ + expr = sympify(expr) + + if is_literal(expr) and not isinstance(expr, Not): + return True + + if isinstance(expr, And): + for arg in expr.args: + if not arg.is_Symbol: + return False + return True + + elif isinstance(expr, Xor): + for arg in expr.args: + if isinstance(arg, And): + for a in arg.args: + if not a.is_Symbol: + return False + elif is_literal(arg): + if isinstance(arg, Not): + return False + else: + return False + return True + + else: + return False + + +def is_nnf(expr, simplified=True): + """ + Checks if ``expr`` is in Negation Normal Form (NNF). + + A logical expression is in NNF if it + contains only :py:class:`~.And`, :py:class:`~.Or` and :py:class:`~.Not`, + and :py:class:`~.Not` is applied only to literals. + If ``simplified`` is ``True``, checks if result contains no redundant clauses. + + Examples + ======== + + >>> from sympy.abc import A, B, C + >>> from sympy.logic.boolalg import Not, is_nnf + >>> is_nnf(A & B | ~C) + True + >>> is_nnf((A | ~A) & (B | C)) + False + >>> is_nnf((A | ~A) & (B | C), False) + True + >>> is_nnf(Not(A & B) | C) + False + >>> is_nnf((A >> B) & (B >> A)) + False + + """ + + expr = sympify(expr) + if is_literal(expr): + return True + + stack = [expr] + + while stack: + expr = stack.pop() + if expr.func in (And, Or): + if simplified: + args = expr.args + for arg in args: + if Not(arg) in args: + return False + stack.extend(expr.args) + + elif not is_literal(expr): + return False + + return True + + +def is_cnf(expr): + """ + Test whether or not an expression is in conjunctive normal form. + + Examples + ======== + + >>> from sympy.logic.boolalg import is_cnf + >>> from sympy.abc import A, B, C + >>> is_cnf(A | B | C) + True + >>> is_cnf(A & B & C) + True + >>> is_cnf((A & B) | C) + False + + """ + return _is_form(expr, And, Or) + + +def is_dnf(expr): + """ + Test whether or not an expression is in disjunctive normal form. + + Examples + ======== + + >>> from sympy.logic.boolalg import is_dnf + >>> from sympy.abc import A, B, C + >>> is_dnf(A | B | C) + True + >>> is_dnf(A & B & C) + True + >>> is_dnf((A & B) | C) + True + >>> is_dnf(A & (B | C)) + False + + """ + return _is_form(expr, Or, And) + + +def _is_form(expr, function1, function2): + """ + Test whether or not an expression is of the required form. + + """ + expr = sympify(expr) + + vals = function1.make_args(expr) if isinstance(expr, function1) else [expr] + for lit in vals: + if isinstance(lit, function2): + vals2 = function2.make_args(lit) if isinstance(lit, function2) else [lit] + for l in vals2: + if is_literal(l) is False: + return False + elif is_literal(lit) is False: + return False + + return True + + +def eliminate_implications(expr): + """ + Change :py:class:`~.Implies` and :py:class:`~.Equivalent` into + :py:class:`~.And`, :py:class:`~.Or`, and :py:class:`~.Not`. + That is, return an expression that is equivalent to ``expr``, but has only + ``&``, ``|``, and ``~`` as logical + operators. + + Examples + ======== + + >>> from sympy.logic.boolalg import Implies, Equivalent, \ + eliminate_implications + >>> from sympy.abc import A, B, C + >>> eliminate_implications(Implies(A, B)) + B | ~A + >>> eliminate_implications(Equivalent(A, B)) + (A | ~B) & (B | ~A) + >>> eliminate_implications(Equivalent(A, B, C)) + (A | ~C) & (B | ~A) & (C | ~B) + + """ + return to_nnf(expr, simplify=False) + + +def is_literal(expr): + """ + Returns True if expr is a literal, else False. + + Examples + ======== + + >>> from sympy import Or, Q + >>> from sympy.abc import A, B + >>> from sympy.logic.boolalg import is_literal + >>> is_literal(A) + True + >>> is_literal(~A) + True + >>> is_literal(Q.zero(A)) + True + >>> is_literal(A + B) + True + >>> is_literal(Or(A, B)) + False + + """ + from sympy.assumptions import AppliedPredicate + + if isinstance(expr, Not): + return is_literal(expr.args[0]) + elif expr in (True, False) or isinstance(expr, AppliedPredicate) or expr.is_Atom: + return True + elif not isinstance(expr, BooleanFunction) and all( + (isinstance(expr, AppliedPredicate) or a.is_Atom) for a in expr.args): + return True + return False + + +def to_int_repr(clauses, symbols): + """ + Takes clauses in CNF format and puts them into an integer representation. + + Examples + ======== + + >>> from sympy.logic.boolalg import to_int_repr + >>> from sympy.abc import x, y + >>> to_int_repr([x | y, y], [x, y]) == [{1, 2}, {2}] + True + + """ + + # Convert the symbol list into a dict + symbols = dict(zip(symbols, range(1, len(symbols) + 1))) + + def append_symbol(arg, symbols): + if isinstance(arg, Not): + return -symbols[arg.args[0]] + else: + return symbols[arg] + + return [{append_symbol(arg, symbols) for arg in Or.make_args(c)} + for c in clauses] + + +def term_to_integer(term): + """ + Return an integer corresponding to the base-2 digits given by *term*. + + Parameters + ========== + + term : a string or list of ones and zeros + + Examples + ======== + + >>> from sympy.logic.boolalg import term_to_integer + >>> term_to_integer([1, 0, 0]) + 4 + >>> term_to_integer('100') + 4 + + """ + + return int(''.join(list(map(str, list(term)))), 2) + + +integer_to_term = ibin # XXX could delete? + + +def truth_table(expr, variables, input=True): + """ + Return a generator of all possible configurations of the input variables, + and the result of the boolean expression for those values. + + Parameters + ========== + + expr : Boolean expression + + variables : list of variables + + input : bool (default ``True``) + Indicates whether to return the input combinations. + + Examples + ======== + + >>> from sympy.logic.boolalg import truth_table + >>> from sympy.abc import x,y + >>> table = truth_table(x >> y, [x, y]) + >>> for t in table: + ... print('{0} -> {1}'.format(*t)) + [0, 0] -> True + [0, 1] -> True + [1, 0] -> False + [1, 1] -> True + + >>> table = truth_table(x | y, [x, y]) + >>> list(table) + [([0, 0], False), ([0, 1], True), ([1, 0], True), ([1, 1], True)] + + If ``input`` is ``False``, ``truth_table`` returns only a list of truth values. + In this case, the corresponding input values of variables can be + deduced from the index of a given output. + + >>> from sympy.utilities.iterables import ibin + >>> vars = [y, x] + >>> values = truth_table(x >> y, vars, input=False) + >>> values = list(values) + >>> values + [True, False, True, True] + + >>> for i, value in enumerate(values): + ... print('{0} -> {1}'.format(list(zip( + ... vars, ibin(i, len(vars)))), value)) + [(y, 0), (x, 0)] -> True + [(y, 0), (x, 1)] -> False + [(y, 1), (x, 0)] -> True + [(y, 1), (x, 1)] -> True + + """ + variables = [sympify(v) for v in variables] + + expr = sympify(expr) + if not isinstance(expr, BooleanFunction) and not is_literal(expr): + return + + table = product((0, 1), repeat=len(variables)) + for term in table: + value = expr.xreplace(dict(zip(variables, term))) + + if input: + yield list(term), value + else: + yield value + + +def _check_pair(minterm1, minterm2): + """ + Checks if a pair of minterms differs by only one bit. If yes, returns + index, else returns `-1`. + """ + # Early termination seems to be faster than list comprehension, + # at least for large examples. + index = -1 + for x, i in enumerate(minterm1): # zip(minterm1, minterm2) is slower + if i != minterm2[x]: + if index == -1: + index = x + else: + return -1 + return index + + +def _convert_to_varsSOP(minterm, variables): + """ + Converts a term in the expansion of a function from binary to its + variable form (for SOP). + """ + temp = [variables[n] if val == 1 else Not(variables[n]) + for n, val in enumerate(minterm) if val != 3] + return And(*temp) + + +def _convert_to_varsPOS(maxterm, variables): + """ + Converts a term in the expansion of a function from binary to its + variable form (for POS). + """ + temp = [variables[n] if val == 0 else Not(variables[n]) + for n, val in enumerate(maxterm) if val != 3] + return Or(*temp) + + +def _convert_to_varsANF(term, variables): + """ + Converts a term in the expansion of a function from binary to its + variable form (for ANF). + + Parameters + ========== + + term : list of 1's and 0's (complementation pattern) + variables : list of variables + + """ + temp = [variables[n] for n, t in enumerate(term) if t == 1] + + if not temp: + return true + + return And(*temp) + + +def _get_odd_parity_terms(n): + """ + Returns a list of lists, with all possible combinations of n zeros and ones + with an odd number of ones. + """ + return [e for e in [ibin(i, n) for i in range(2**n)] if sum(e) % 2 == 1] + + +def _get_even_parity_terms(n): + """ + Returns a list of lists, with all possible combinations of n zeros and ones + with an even number of ones. + """ + return [e for e in [ibin(i, n) for i in range(2**n)] if sum(e) % 2 == 0] + + +def _simplified_pairs(terms): + """ + Reduces a set of minterms, if possible, to a simplified set of minterms + with one less variable in the terms using QM method. + """ + if not terms: + return [] + + simplified_terms = [] + todo = list(range(len(terms))) + + # Count number of ones as _check_pair can only potentially match if there + # is at most a difference of a single one + termdict = defaultdict(list) + for n, term in enumerate(terms): + ones = sum([1 for t in term if t == 1]) + termdict[ones].append(n) + + variables = len(terms[0]) + for k in range(variables): + for i in termdict[k]: + for j in termdict[k+1]: + index = _check_pair(terms[i], terms[j]) + if index != -1: + # Mark terms handled + todo[i] = todo[j] = None + # Copy old term + newterm = terms[i][:] + # Set differing position to don't care + newterm[index] = 3 + # Add if not already there + if newterm not in simplified_terms: + simplified_terms.append(newterm) + + if simplified_terms: + # Further simplifications only among the new terms + simplified_terms = _simplified_pairs(simplified_terms) + + # Add remaining, non-simplified, terms + simplified_terms.extend([terms[i] for i in todo if i is not None]) + return simplified_terms + + +def _rem_redundancy(l1, terms): + """ + After the truth table has been sufficiently simplified, use the prime + implicant table method to recognize and eliminate redundant pairs, + and return the essential arguments. + """ + + if not terms: + return [] + + nterms = len(terms) + nl1 = len(l1) + + # Create dominating matrix + dommatrix = [[0]*nl1 for n in range(nterms)] + colcount = [0]*nl1 + rowcount = [0]*nterms + for primei, prime in enumerate(l1): + for termi, term in enumerate(terms): + # Check prime implicant covering term + if all(t == 3 or t == mt for t, mt in zip(prime, term)): + dommatrix[termi][primei] = 1 + colcount[primei] += 1 + rowcount[termi] += 1 + + # Keep track if anything changed + anythingchanged = True + # Then, go again + while anythingchanged: + anythingchanged = False + + for rowi in range(nterms): + # Still non-dominated? + if rowcount[rowi]: + row = dommatrix[rowi] + for row2i in range(nterms): + # Still non-dominated? + if rowi != row2i and rowcount[rowi] and (rowcount[rowi] <= rowcount[row2i]): + row2 = dommatrix[row2i] + if all(row2[n] >= row[n] for n in range(nl1)): + # row2 dominating row, remove row2 + rowcount[row2i] = 0 + anythingchanged = True + for primei, prime in enumerate(row2): + if prime: + # Make corresponding entry 0 + dommatrix[row2i][primei] = 0 + colcount[primei] -= 1 + + colcache = {} + + for coli in range(nl1): + # Still non-dominated? + if colcount[coli]: + if coli in colcache: + col = colcache[coli] + else: + col = [dommatrix[i][coli] for i in range(nterms)] + colcache[coli] = col + for col2i in range(nl1): + # Still non-dominated? + if coli != col2i and colcount[col2i] and (colcount[coli] >= colcount[col2i]): + if col2i in colcache: + col2 = colcache[col2i] + else: + col2 = [dommatrix[i][col2i] for i in range(nterms)] + colcache[col2i] = col2 + if all(col[n] >= col2[n] for n in range(nterms)): + # col dominating col2, remove col2 + colcount[col2i] = 0 + anythingchanged = True + for termi, term in enumerate(col2): + if term and dommatrix[termi][col2i]: + # Make corresponding entry 0 + dommatrix[termi][col2i] = 0 + rowcount[termi] -= 1 + + if not anythingchanged: + # Heuristically select the prime implicant covering most terms + maxterms = 0 + bestcolidx = -1 + for coli in range(nl1): + s = colcount[coli] + if s > maxterms: + bestcolidx = coli + maxterms = s + + # In case we found a prime implicant covering at least two terms + if bestcolidx != -1 and maxterms > 1: + for primei, prime in enumerate(l1): + if primei != bestcolidx: + for termi, term in enumerate(colcache[bestcolidx]): + if term and dommatrix[termi][primei]: + # Make corresponding entry 0 + dommatrix[termi][primei] = 0 + anythingchanged = True + rowcount[termi] -= 1 + colcount[primei] -= 1 + + return [l1[i] for i in range(nl1) if colcount[i]] + + +def _input_to_binlist(inputlist, variables): + binlist = [] + bits = len(variables) + for val in inputlist: + if isinstance(val, int): + binlist.append(ibin(val, bits)) + elif isinstance(val, dict): + nonspecvars = list(variables) + for key in val.keys(): + nonspecvars.remove(key) + for t in product((0, 1), repeat=len(nonspecvars)): + d = dict(zip(nonspecvars, t)) + d.update(val) + binlist.append([d[v] for v in variables]) + elif isinstance(val, (list, tuple)): + if len(val) != bits: + raise ValueError("Each term must contain {bits} bits as there are" + "\n{bits} variables (or be an integer)." + "".format(bits=bits)) + binlist.append(list(val)) + else: + raise TypeError("A term list can only contain lists," + " ints or dicts.") + return binlist + + +def SOPform(variables, minterms, dontcares=None): + """ + The SOPform function uses simplified_pairs and a redundant group- + eliminating algorithm to convert the list of all input combos that + generate '1' (the minterms) into the smallest sum-of-products form. + + The variables must be given as the first argument. + + Return a logical :py:class:`~.Or` function (i.e., the "sum of products" or + "SOP" form) that gives the desired outcome. If there are inputs that can + be ignored, pass them as a list, too. + + The result will be one of the (perhaps many) functions that satisfy + the conditions. + + Examples + ======== + + >>> from sympy.logic import SOPform + >>> from sympy import symbols + >>> w, x, y, z = symbols('w x y z') + >>> minterms = [[0, 0, 0, 1], [0, 0, 1, 1], + ... [0, 1, 1, 1], [1, 0, 1, 1], [1, 1, 1, 1]] + >>> dontcares = [[0, 0, 0, 0], [0, 0, 1, 0], [0, 1, 0, 1]] + >>> SOPform([w, x, y, z], minterms, dontcares) + (y & z) | (~w & ~x) + + The terms can also be represented as integers: + + >>> minterms = [1, 3, 7, 11, 15] + >>> dontcares = [0, 2, 5] + >>> SOPform([w, x, y, z], minterms, dontcares) + (y & z) | (~w & ~x) + + They can also be specified using dicts, which does not have to be fully + specified: + + >>> minterms = [{w: 0, x: 1}, {y: 1, z: 1, x: 0}] + >>> SOPform([w, x, y, z], minterms) + (x & ~w) | (y & z & ~x) + + Or a combination: + + >>> minterms = [4, 7, 11, [1, 1, 1, 1]] + >>> dontcares = [{w : 0, x : 0, y: 0}, 5] + >>> SOPform([w, x, y, z], minterms, dontcares) + (w & y & z) | (~w & ~y) | (x & z & ~w) + + See also + ======== + + POSform + + References + ========== + + .. [1] https://en.wikipedia.org/wiki/Quine-McCluskey_algorithm + .. [2] https://en.wikipedia.org/wiki/Don%27t-care_term + + """ + if not minterms: + return false + + variables = tuple(map(sympify, variables)) + + + minterms = _input_to_binlist(minterms, variables) + dontcares = _input_to_binlist((dontcares or []), variables) + for d in dontcares: + if d in minterms: + raise ValueError('%s in minterms is also in dontcares' % d) + + return _sop_form(variables, minterms, dontcares) + + +def _sop_form(variables, minterms, dontcares): + new = _simplified_pairs(minterms + dontcares) + essential = _rem_redundancy(new, minterms) + return Or(*[_convert_to_varsSOP(x, variables) for x in essential]) + + +def POSform(variables, minterms, dontcares=None): + """ + The POSform function uses simplified_pairs and a redundant-group + eliminating algorithm to convert the list of all input combinations + that generate '1' (the minterms) into the smallest product-of-sums form. + + The variables must be given as the first argument. + + Return a logical :py:class:`~.And` function (i.e., the "product of sums" + or "POS" form) that gives the desired outcome. If there are inputs that can + be ignored, pass them as a list, too. + + The result will be one of the (perhaps many) functions that satisfy + the conditions. + + Examples + ======== + + >>> from sympy.logic import POSform + >>> from sympy import symbols + >>> w, x, y, z = symbols('w x y z') + >>> minterms = [[0, 0, 0, 1], [0, 0, 1, 1], [0, 1, 1, 1], + ... [1, 0, 1, 1], [1, 1, 1, 1]] + >>> dontcares = [[0, 0, 0, 0], [0, 0, 1, 0], [0, 1, 0, 1]] + >>> POSform([w, x, y, z], minterms, dontcares) + z & (y | ~w) + + The terms can also be represented as integers: + + >>> minterms = [1, 3, 7, 11, 15] + >>> dontcares = [0, 2, 5] + >>> POSform([w, x, y, z], minterms, dontcares) + z & (y | ~w) + + They can also be specified using dicts, which does not have to be fully + specified: + + >>> minterms = [{w: 0, x: 1}, {y: 1, z: 1, x: 0}] + >>> POSform([w, x, y, z], minterms) + (x | y) & (x | z) & (~w | ~x) + + Or a combination: + + >>> minterms = [4, 7, 11, [1, 1, 1, 1]] + >>> dontcares = [{w : 0, x : 0, y: 0}, 5] + >>> POSform([w, x, y, z], minterms, dontcares) + (w | x) & (y | ~w) & (z | ~y) + + See also + ======== + + SOPform + + References + ========== + + .. [1] https://en.wikipedia.org/wiki/Quine-McCluskey_algorithm + .. [2] https://en.wikipedia.org/wiki/Don%27t-care_term + + """ + if not minterms: + return false + + variables = tuple(map(sympify, variables)) + minterms = _input_to_binlist(minterms, variables) + dontcares = _input_to_binlist((dontcares or []), variables) + for d in dontcares: + if d in minterms: + raise ValueError('%s in minterms is also in dontcares' % d) + + maxterms = [] + for t in product((0, 1), repeat=len(variables)): + t = list(t) + if (t not in minterms) and (t not in dontcares): + maxterms.append(t) + + new = _simplified_pairs(maxterms + dontcares) + essential = _rem_redundancy(new, maxterms) + return And(*[_convert_to_varsPOS(x, variables) for x in essential]) + + +def ANFform(variables, truthvalues): + """ + The ANFform function converts the list of truth values to + Algebraic Normal Form (ANF). + + The variables must be given as the first argument. + + Return True, False, logical :py:class:`~.And` function (i.e., the + "Zhegalkin monomial") or logical :py:class:`~.Xor` function (i.e., + the "Zhegalkin polynomial"). When True and False + are represented by 1 and 0, respectively, then + :py:class:`~.And` is multiplication and :py:class:`~.Xor` is addition. + + Formally a "Zhegalkin monomial" is the product (logical + And) of a finite set of distinct variables, including + the empty set whose product is denoted 1 (True). + A "Zhegalkin polynomial" is the sum (logical Xor) of a + set of Zhegalkin monomials, with the empty set denoted + by 0 (False). + + Parameters + ========== + + variables : list of variables + truthvalues : list of 1's and 0's (result column of truth table) + + Examples + ======== + >>> from sympy.logic.boolalg import ANFform + >>> from sympy.abc import x, y + >>> ANFform([x], [1, 0]) + x ^ True + >>> ANFform([x, y], [0, 1, 1, 1]) + x ^ y ^ (x & y) + + References + ========== + + .. [1] https://en.wikipedia.org/wiki/Zhegalkin_polynomial + + """ + + n_vars = len(variables) + n_values = len(truthvalues) + + if n_values != 2 ** n_vars: + raise ValueError("The number of truth values must be equal to 2^%d, " + "got %d" % (n_vars, n_values)) + + variables = tuple(map(sympify, variables)) + + coeffs = anf_coeffs(truthvalues) + terms = [] + + for i, t in enumerate(product((0, 1), repeat=n_vars)): + if coeffs[i] == 1: + terms.append(t) + + return Xor(*[_convert_to_varsANF(x, variables) for x in terms], + remove_true=False) + + +def anf_coeffs(truthvalues): + """ + Convert a list of truth values of some boolean expression + to the list of coefficients of the polynomial mod 2 (exclusive + disjunction) representing the boolean expression in ANF + (i.e., the "Zhegalkin polynomial"). + + There are `2^n` possible Zhegalkin monomials in `n` variables, since + each monomial is fully specified by the presence or absence of + each variable. + + We can enumerate all the monomials. For example, boolean + function with four variables ``(a, b, c, d)`` can contain + up to `2^4 = 16` monomials. The 13-th monomial is the + product ``a & b & d``, because 13 in binary is 1, 1, 0, 1. + + A given monomial's presence or absence in a polynomial corresponds + to that monomial's coefficient being 1 or 0 respectively. + + Examples + ======== + >>> from sympy.logic.boolalg import anf_coeffs, bool_monomial, Xor + >>> from sympy.abc import a, b, c + >>> truthvalues = [0, 1, 1, 0, 0, 1, 0, 1] + >>> coeffs = anf_coeffs(truthvalues) + >>> coeffs + [0, 1, 1, 0, 0, 0, 1, 0] + >>> polynomial = Xor(*[ + ... bool_monomial(k, [a, b, c]) + ... for k, coeff in enumerate(coeffs) if coeff == 1 + ... ]) + >>> polynomial + b ^ c ^ (a & b) + + """ + + s = '{:b}'.format(len(truthvalues)) + n = len(s) - 1 + + if len(truthvalues) != 2**n: + raise ValueError("The number of truth values must be a power of two, " + "got %d" % len(truthvalues)) + + coeffs = [[v] for v in truthvalues] + + for i in range(n): + tmp = [] + for j in range(2 ** (n-i-1)): + tmp.append(coeffs[2*j] + + list(map(lambda x, y: x^y, coeffs[2*j], coeffs[2*j+1]))) + coeffs = tmp + + return coeffs[0] + + +def bool_minterm(k, variables): + """ + Return the k-th minterm. + + Minterms are numbered by a binary encoding of the complementation + pattern of the variables. This convention assigns the value 1 to + the direct form and 0 to the complemented form. + + Parameters + ========== + + k : int or list of 1's and 0's (complementation pattern) + variables : list of variables + + Examples + ======== + + >>> from sympy.logic.boolalg import bool_minterm + >>> from sympy.abc import x, y, z + >>> bool_minterm([1, 0, 1], [x, y, z]) + x & z & ~y + >>> bool_minterm(6, [x, y, z]) + x & y & ~z + + References + ========== + + .. [1] https://en.wikipedia.org/wiki/Canonical_normal_form#Indexing_minterms + + """ + if isinstance(k, int): + k = ibin(k, len(variables)) + variables = tuple(map(sympify, variables)) + return _convert_to_varsSOP(k, variables) + + +def bool_maxterm(k, variables): + """ + Return the k-th maxterm. + + Each maxterm is assigned an index based on the opposite + conventional binary encoding used for minterms. The maxterm + convention assigns the value 0 to the direct form and 1 to + the complemented form. + + Parameters + ========== + + k : int or list of 1's and 0's (complementation pattern) + variables : list of variables + + Examples + ======== + >>> from sympy.logic.boolalg import bool_maxterm + >>> from sympy.abc import x, y, z + >>> bool_maxterm([1, 0, 1], [x, y, z]) + y | ~x | ~z + >>> bool_maxterm(6, [x, y, z]) + z | ~x | ~y + + References + ========== + + .. [1] https://en.wikipedia.org/wiki/Canonical_normal_form#Indexing_maxterms + + """ + if isinstance(k, int): + k = ibin(k, len(variables)) + variables = tuple(map(sympify, variables)) + return _convert_to_varsPOS(k, variables) + + +def bool_monomial(k, variables): + """ + Return the k-th monomial. + + Monomials are numbered by a binary encoding of the presence and + absences of the variables. This convention assigns the value + 1 to the presence of variable and 0 to the absence of variable. + + Each boolean function can be uniquely represented by a + Zhegalkin Polynomial (Algebraic Normal Form). The Zhegalkin + Polynomial of the boolean function with `n` variables can contain + up to `2^n` monomials. We can enumerate all the monomials. + Each monomial is fully specified by the presence or absence + of each variable. + + For example, boolean function with four variables ``(a, b, c, d)`` + can contain up to `2^4 = 16` monomials. The 13-th monomial is the + product ``a & b & d``, because 13 in binary is 1, 1, 0, 1. + + Parameters + ========== + + k : int or list of 1's and 0's + variables : list of variables + + Examples + ======== + >>> from sympy.logic.boolalg import bool_monomial + >>> from sympy.abc import x, y, z + >>> bool_monomial([1, 0, 1], [x, y, z]) + x & z + >>> bool_monomial(6, [x, y, z]) + x & y + + """ + if isinstance(k, int): + k = ibin(k, len(variables)) + variables = tuple(map(sympify, variables)) + return _convert_to_varsANF(k, variables) + + +def _find_predicates(expr): + """Helper to find logical predicates in BooleanFunctions. + + A logical predicate is defined here as anything within a BooleanFunction + that is not a BooleanFunction itself. + + """ + if not isinstance(expr, BooleanFunction): + return {expr} + return set().union(*(map(_find_predicates, expr.args))) + + +def simplify_logic(expr, form=None, deep=True, force=False, dontcare=None): + """ + This function simplifies a boolean function to its simplified version + in SOP or POS form. The return type is an :py:class:`~.Or` or + :py:class:`~.And` object in SymPy. + + Parameters + ========== + + expr : Boolean + + form : string (``'cnf'`` or ``'dnf'``) or ``None`` (default). + If ``'cnf'`` or ``'dnf'``, the simplest expression in the corresponding + normal form is returned; if ``None``, the answer is returned + according to the form with fewest args (in CNF by default). + + deep : bool (default ``True``) + Indicates whether to recursively simplify any + non-boolean functions contained within the input. + + force : bool (default ``False``) + As the simplifications require exponential time in the number + of variables, there is by default a limit on expressions with + 8 variables. When the expression has more than 8 variables + only symbolical simplification (controlled by ``deep``) is + made. By setting ``force`` to ``True``, this limit is removed. Be + aware that this can lead to very long simplification times. + + dontcare : Boolean + Optimize expression under the assumption that inputs where this + expression is true are don't care. This is useful in e.g. Piecewise + conditions, where later conditions do not need to consider inputs that + are converted by previous conditions. For example, if a previous + condition is ``And(A, B)``, the simplification of expr can be made + with don't cares for ``And(A, B)``. + + Examples + ======== + + >>> from sympy.logic import simplify_logic + >>> from sympy.abc import x, y, z + >>> b = (~x & ~y & ~z) | ( ~x & ~y & z) + >>> simplify_logic(b) + ~x & ~y + >>> simplify_logic(x | y, dontcare=y) + x + + References + ========== + + .. [1] https://en.wikipedia.org/wiki/Don%27t-care_term + + """ + + if form not in (None, 'cnf', 'dnf'): + raise ValueError("form can be cnf or dnf only") + expr = sympify(expr) + # check for quick exit if form is given: right form and all args are + # literal and do not involve Not + if form: + form_ok = False + if form == 'cnf': + form_ok = is_cnf(expr) + elif form == 'dnf': + form_ok = is_dnf(expr) + + if form_ok and all(is_literal(a) + for a in expr.args): + return expr + from sympy.core.relational import Relational + if deep: + variables = expr.atoms(Relational) + from sympy.simplify.simplify import simplify + s = tuple(map(simplify, variables)) + expr = expr.xreplace(dict(zip(variables, s))) + if not isinstance(expr, BooleanFunction): + return expr + # Replace Relationals with Dummys to possibly + # reduce the number of variables + repl = {} + undo = {} + from sympy.core.symbol import Dummy + variables = expr.atoms(Relational) + if dontcare is not None: + dontcare = sympify(dontcare) + variables.update(dontcare.atoms(Relational)) + while variables: + var = variables.pop() + if var.is_Relational: + d = Dummy() + undo[d] = var + repl[var] = d + nvar = var.negated + if nvar in variables: + repl[nvar] = Not(d) + variables.remove(nvar) + + expr = expr.xreplace(repl) + + if dontcare is not None: + dontcare = dontcare.xreplace(repl) + + # Get new variables after replacing + variables = _find_predicates(expr) + if not force and len(variables) > 8: + return expr.xreplace(undo) + if dontcare is not None: + # Add variables from dontcare + dcvariables = _find_predicates(dontcare) + variables.update(dcvariables) + # if too many restore to variables only + if not force and len(variables) > 8: + variables = _find_predicates(expr) + dontcare = None + # group into constants and variable values + c, v = sift(ordered(variables), lambda x: x in (True, False), binary=True) + variables = c + v + # standardize constants to be 1 or 0 in keeping with truthtable + c = [1 if i == True else 0 for i in c] + truthtable = _get_truthtable(v, expr, c) + if dontcare is not None: + dctruthtable = _get_truthtable(v, dontcare, c) + truthtable = [t for t in truthtable if t not in dctruthtable] + else: + dctruthtable = [] + big = len(truthtable) >= (2 ** (len(variables) - 1)) + if form == 'dnf' or form is None and big: + return _sop_form(variables, truthtable, dctruthtable).xreplace(undo) + return POSform(variables, truthtable, dctruthtable).xreplace(undo) + + +def _get_truthtable(variables, expr, const): + """ Return a list of all combinations leading to a True result for ``expr``. + """ + _variables = variables.copy() + def _get_tt(inputs): + if _variables: + v = _variables.pop() + tab = [[i[0].xreplace({v: false}), [0] + i[1]] for i in inputs if i[0] is not false] + tab.extend([[i[0].xreplace({v: true}), [1] + i[1]] for i in inputs if i[0] is not false]) + return _get_tt(tab) + return inputs + res = [const + k[1] for k in _get_tt([[expr, []]]) if k[0]] + if res == [[]]: + return [] + else: + return res + + +def _finger(eq): + """ + Assign a 5-item fingerprint to each symbol in the equation: + [ + # of times it appeared as a Symbol; + # of times it appeared as a Not(symbol); + # of times it appeared as a Symbol in an And or Or; + # of times it appeared as a Not(Symbol) in an And or Or; + a sorted tuple of tuples, (i, j, k), where i is the number of arguments + in an And or Or with which it appeared as a Symbol, and j is + the number of arguments that were Not(Symbol); k is the number + of times that (i, j) was seen. + ] + + Examples + ======== + + >>> from sympy.logic.boolalg import _finger as finger + >>> from sympy import And, Or, Not, Xor, to_cnf, symbols + >>> from sympy.abc import a, b, x, y + >>> eq = Or(And(Not(y), a), And(Not(y), b), And(x, y)) + >>> dict(finger(eq)) + {(0, 0, 1, 0, ((2, 0, 1),)): [x], + (0, 0, 1, 0, ((2, 1, 1),)): [a, b], + (0, 0, 1, 2, ((2, 0, 1),)): [y]} + >>> dict(finger(x & ~y)) + {(0, 1, 0, 0, ()): [y], (1, 0, 0, 0, ()): [x]} + + In the following, the (5, 2, 6) means that there were 6 Or + functions in which a symbol appeared as itself amongst 5 arguments in + which there were also 2 negated symbols, e.g. ``(a0 | a1 | a2 | ~a3 | ~a4)`` + is counted once for a0, a1 and a2. + + >>> dict(finger(to_cnf(Xor(*symbols('a:5'))))) + {(0, 0, 8, 8, ((5, 0, 1), (5, 2, 6), (5, 4, 1))): [a0, a1, a2, a3, a4]} + + The equation must not have more than one level of nesting: + + >>> dict(finger(And(Or(x, y), y))) + {(0, 0, 1, 0, ((2, 0, 1),)): [x], (1, 0, 1, 0, ((2, 0, 1),)): [y]} + >>> dict(finger(And(Or(x, And(a, x)), y))) + Traceback (most recent call last): + ... + NotImplementedError: unexpected level of nesting + + So y and x have unique fingerprints, but a and b do not. + """ + f = eq.free_symbols + d = dict(list(zip(f, [[0]*4 + [defaultdict(int)] for fi in f]))) + for a in eq.args: + if a.is_Symbol: + d[a][0] += 1 + elif a.is_Not: + d[a.args[0]][1] += 1 + else: + o = len(a.args), sum(isinstance(ai, Not) for ai in a.args) + for ai in a.args: + if ai.is_Symbol: + d[ai][2] += 1 + d[ai][-1][o] += 1 + elif ai.is_Not: + d[ai.args[0]][3] += 1 + else: + raise NotImplementedError('unexpected level of nesting') + inv = defaultdict(list) + for k, v in ordered(iter(d.items())): + v[-1] = tuple(sorted([i + (j,) for i, j in v[-1].items()])) + inv[tuple(v)].append(k) + return inv + + +def bool_map(bool1, bool2): + """ + Return the simplified version of *bool1*, and the mapping of variables + that makes the two expressions *bool1* and *bool2* represent the same + logical behaviour for some correspondence between the variables + of each. + If more than one mappings of this sort exist, one of them + is returned. + + For example, ``And(x, y)`` is logically equivalent to ``And(a, b)`` for + the mapping ``{x: a, y: b}`` or ``{x: b, y: a}``. + If no such mapping exists, return ``False``. + + Examples + ======== + + >>> from sympy import SOPform, bool_map, Or, And, Not, Xor + >>> from sympy.abc import w, x, y, z, a, b, c, d + >>> function1 = SOPform([x, z, y],[[1, 0, 1], [0, 0, 1]]) + >>> function2 = SOPform([a, b, c],[[1, 0, 1], [1, 0, 0]]) + >>> bool_map(function1, function2) + (y & ~z, {y: a, z: b}) + + The results are not necessarily unique, but they are canonical. Here, + ``(w, z)`` could be ``(a, d)`` or ``(d, a)``: + + >>> eq = Or(And(Not(y), w), And(Not(y), z), And(x, y)) + >>> eq2 = Or(And(Not(c), a), And(Not(c), d), And(b, c)) + >>> bool_map(eq, eq2) + ((x & y) | (w & ~y) | (z & ~y), {w: a, x: b, y: c, z: d}) + >>> eq = And(Xor(a, b), c, And(c,d)) + >>> bool_map(eq, eq.subs(c, x)) + (c & d & (a | b) & (~a | ~b), {a: a, b: b, c: d, d: x}) + + """ + + def match(function1, function2): + """Return the mapping that equates variables between two + simplified boolean expressions if possible. + + By "simplified" we mean that a function has been denested + and is either an And (or an Or) whose arguments are either + symbols (x), negated symbols (Not(x)), or Or (or an And) whose + arguments are only symbols or negated symbols. For example, + ``And(x, Not(y), Or(w, Not(z)))``. + + Basic.match is not robust enough (see issue 4835) so this is + a workaround that is valid for simplified boolean expressions + """ + + # do some quick checks + if function1.__class__ != function2.__class__: + return None # maybe simplification makes them the same? + if len(function1.args) != len(function2.args): + return None # maybe simplification makes them the same? + if function1.is_Symbol: + return {function1: function2} + + # get the fingerprint dictionaries + f1 = _finger(function1) + f2 = _finger(function2) + + # more quick checks + if len(f1) != len(f2): + return False + + # assemble the match dictionary if possible + matchdict = {} + for k in f1.keys(): + if k not in f2: + return False + if len(f1[k]) != len(f2[k]): + return False + for i, x in enumerate(f1[k]): + matchdict[x] = f2[k][i] + return matchdict + + a = simplify_logic(bool1) + b = simplify_logic(bool2) + m = match(a, b) + if m: + return a, m + return m + + +def _apply_patternbased_simplification(rv, patterns, measure, + dominatingvalue, + replacementvalue=None, + threeterm_patterns=None): + """ + Replace patterns of Relational + + Parameters + ========== + + rv : Expr + Boolean expression + + patterns : tuple + Tuple of tuples, with (pattern to simplify, simplified pattern) with + two terms. + + measure : function + Simplification measure. + + dominatingvalue : Boolean or ``None`` + The dominating value for the function of consideration. + For example, for :py:class:`~.And` ``S.false`` is dominating. + As soon as one expression is ``S.false`` in :py:class:`~.And`, + the whole expression is ``S.false``. + + replacementvalue : Boolean or ``None``, optional + The resulting value for the whole expression if one argument + evaluates to ``dominatingvalue``. + For example, for :py:class:`~.Nand` ``S.false`` is dominating, but + in this case the resulting value is ``S.true``. Default is ``None``. + If ``replacementvalue`` is ``None`` and ``dominatingvalue`` is not + ``None``, ``replacementvalue = dominatingvalue``. + + threeterm_patterns : tuple, optional + Tuple of tuples, with (pattern to simplify, simplified pattern) with + three terms. + + """ + from sympy.core.relational import Relational, _canonical + + if replacementvalue is None and dominatingvalue is not None: + replacementvalue = dominatingvalue + # Use replacement patterns for Relationals + Rel, nonRel = sift(rv.args, lambda i: isinstance(i, Relational), + binary=True) + if len(Rel) <= 1: + return rv + Rel, nonRealRel = sift(Rel, lambda i: not any(s.is_real is False + for s in i.free_symbols), + binary=True) + Rel = [i.canonical for i in Rel] + + if threeterm_patterns and len(Rel) >= 3: + Rel = _apply_patternbased_threeterm_simplification(Rel, + threeterm_patterns, rv.func, dominatingvalue, + replacementvalue, measure) + + Rel = _apply_patternbased_twoterm_simplification(Rel, patterns, + rv.func, dominatingvalue, replacementvalue, measure) + + rv = rv.func(*([_canonical(i) for i in ordered(Rel)] + + nonRel + nonRealRel)) + return rv + + +def _apply_patternbased_twoterm_simplification(Rel, patterns, func, + dominatingvalue, + replacementvalue, + measure): + """ Apply pattern-based two-term simplification.""" + from sympy.functions.elementary.miscellaneous import Min, Max + from sympy.core.relational import Ge, Gt, _Inequality + changed = True + while changed and len(Rel) >= 2: + changed = False + # Use only < or <= + Rel = [r.reversed if isinstance(r, (Ge, Gt)) else r for r in Rel] + # Sort based on ordered + Rel = list(ordered(Rel)) + # Eq and Ne must be tested reversed as well + rtmp = [(r, ) if isinstance(r, _Inequality) else (r, r.reversed) for r in Rel] + # Create a list of possible replacements + results = [] + # Try all combinations of possibly reversed relational + for ((i, pi), (j, pj)) in combinations(enumerate(rtmp), 2): + for pattern, simp in patterns: + res = [] + for p1, p2 in product(pi, pj): + # use SymPy matching + oldexpr = Tuple(p1, p2) + tmpres = oldexpr.match(pattern) + if tmpres: + res.append((tmpres, oldexpr)) + + if res: + for tmpres, oldexpr in res: + # we have a matching, compute replacement + np = simp.xreplace(tmpres) + if np == dominatingvalue: + # if dominatingvalue, the whole expression + # will be replacementvalue + return [replacementvalue] + # add replacement + if not isinstance(np, ITE) and not np.has(Min, Max): + # We only want to use ITE and Min/Max replacements if + # they simplify to a relational + costsaving = measure(func(*oldexpr.args)) - measure(np) + if costsaving > 0: + results.append((costsaving, ([i, j], np))) + if results: + # Sort results based on complexity + results = sorted(results, + key=lambda pair: pair[0], reverse=True) + # Replace the one providing most simplification + replacement = results[0][1] + idx, newrel = replacement + idx.sort() + # Remove the old relationals + for index in reversed(idx): + del Rel[index] + if dominatingvalue is None or newrel != Not(dominatingvalue): + # Insert the new one (no need to insert a value that will + # not affect the result) + if newrel.func == func: + for a in newrel.args: + Rel.append(a) + else: + Rel.append(newrel) + # We did change something so try again + changed = True + return Rel + + +def _apply_patternbased_threeterm_simplification(Rel, patterns, func, + dominatingvalue, + replacementvalue, + measure): + """ Apply pattern-based three-term simplification.""" + from sympy.functions.elementary.miscellaneous import Min, Max + from sympy.core.relational import Le, Lt, _Inequality + changed = True + while changed and len(Rel) >= 3: + changed = False + # Use only > or >= + Rel = [r.reversed if isinstance(r, (Le, Lt)) else r for r in Rel] + # Sort based on ordered + Rel = list(ordered(Rel)) + # Create a list of possible replacements + results = [] + # Eq and Ne must be tested reversed as well + rtmp = [(r, ) if isinstance(r, _Inequality) else (r, r.reversed) for r in Rel] + # Try all combinations of possibly reversed relational + for ((i, pi), (j, pj), (k, pk)) in permutations(enumerate(rtmp), 3): + for pattern, simp in patterns: + res = [] + for p1, p2, p3 in product(pi, pj, pk): + # use SymPy matching + oldexpr = Tuple(p1, p2, p3) + tmpres = oldexpr.match(pattern) + if tmpres: + res.append((tmpres, oldexpr)) + + if res: + for tmpres, oldexpr in res: + # we have a matching, compute replacement + np = simp.xreplace(tmpres) + if np == dominatingvalue: + # if dominatingvalue, the whole expression + # will be replacementvalue + return [replacementvalue] + # add replacement + if not isinstance(np, ITE) and not np.has(Min, Max): + # We only want to use ITE and Min/Max replacements if + # they simplify to a relational + costsaving = measure(func(*oldexpr.args)) - measure(np) + if costsaving > 0: + results.append((costsaving, ([i, j, k], np))) + if results: + # Sort results based on complexity + results = sorted(results, + key=lambda pair: pair[0], reverse=True) + # Replace the one providing most simplification + replacement = results[0][1] + idx, newrel = replacement + idx.sort() + # Remove the old relationals + for index in reversed(idx): + del Rel[index] + if dominatingvalue is None or newrel != Not(dominatingvalue): + # Insert the new one (no need to insert a value that will + # not affect the result) + if newrel.func == func: + for a in newrel.args: + Rel.append(a) + else: + Rel.append(newrel) + # We did change something so try again + changed = True + return Rel + + +@cacheit +def _simplify_patterns_and(): + """ Two-term patterns for And.""" + + from sympy.core import Wild + from sympy.core.relational import Eq, Ne, Ge, Gt, Le, Lt + from sympy.functions.elementary.complexes import Abs + from sympy.functions.elementary.miscellaneous import Min, Max + a = Wild('a') + b = Wild('b') + c = Wild('c') + # Relationals patterns should be in alphabetical order + # (pattern1, pattern2, simplified) + # Do not use Ge, Gt + _matchers_and = ((Tuple(Eq(a, b), Lt(a, b)), false), + #(Tuple(Eq(a, b), Lt(b, a)), S.false), + #(Tuple(Le(b, a), Lt(a, b)), S.false), + #(Tuple(Lt(b, a), Le(a, b)), S.false), + (Tuple(Lt(b, a), Lt(a, b)), false), + (Tuple(Eq(a, b), Le(b, a)), Eq(a, b)), + #(Tuple(Eq(a, b), Le(a, b)), Eq(a, b)), + #(Tuple(Le(b, a), Lt(b, a)), Gt(a, b)), + (Tuple(Le(b, a), Le(a, b)), Eq(a, b)), + #(Tuple(Le(b, a), Ne(a, b)), Gt(a, b)), + #(Tuple(Lt(b, a), Ne(a, b)), Gt(a, b)), + (Tuple(Le(a, b), Lt(a, b)), Lt(a, b)), + (Tuple(Le(a, b), Ne(a, b)), Lt(a, b)), + (Tuple(Lt(a, b), Ne(a, b)), Lt(a, b)), + # Sign + (Tuple(Eq(a, b), Eq(a, -b)), And(Eq(a, S.Zero), Eq(b, S.Zero))), + # Min/Max/ITE + (Tuple(Le(b, a), Le(c, a)), Ge(a, Max(b, c))), + (Tuple(Le(b, a), Lt(c, a)), ITE(b > c, Ge(a, b), Gt(a, c))), + (Tuple(Lt(b, a), Lt(c, a)), Gt(a, Max(b, c))), + (Tuple(Le(a, b), Le(a, c)), Le(a, Min(b, c))), + (Tuple(Le(a, b), Lt(a, c)), ITE(b < c, Le(a, b), Lt(a, c))), + (Tuple(Lt(a, b), Lt(a, c)), Lt(a, Min(b, c))), + (Tuple(Le(a, b), Le(c, a)), ITE(Eq(b, c), Eq(a, b), ITE(b < c, false, And(Le(a, b), Ge(a, c))))), + (Tuple(Le(c, a), Le(a, b)), ITE(Eq(b, c), Eq(a, b), ITE(b < c, false, And(Le(a, b), Ge(a, c))))), + (Tuple(Lt(a, b), Lt(c, a)), ITE(b < c, false, And(Lt(a, b), Gt(a, c)))), + (Tuple(Lt(c, a), Lt(a, b)), ITE(b < c, false, And(Lt(a, b), Gt(a, c)))), + (Tuple(Le(a, b), Lt(c, a)), ITE(b <= c, false, And(Le(a, b), Gt(a, c)))), + (Tuple(Le(c, a), Lt(a, b)), ITE(b <= c, false, And(Lt(a, b), Ge(a, c)))), + (Tuple(Eq(a, b), Eq(a, c)), ITE(Eq(b, c), Eq(a, b), false)), + (Tuple(Lt(a, b), Lt(-b, a)), ITE(b > 0, Lt(Abs(a), b), false)), + (Tuple(Le(a, b), Le(-b, a)), ITE(b >= 0, Le(Abs(a), b), false)), + ) + return _matchers_and + + +@cacheit +def _simplify_patterns_and3(): + """ Three-term patterns for And.""" + + from sympy.core import Wild + from sympy.core.relational import Eq, Ge, Gt + + a = Wild('a') + b = Wild('b') + c = Wild('c') + # Relationals patterns should be in alphabetical order + # (pattern1, pattern2, pattern3, simplified) + # Do not use Le, Lt + _matchers_and = ((Tuple(Ge(a, b), Ge(b, c), Gt(c, a)), false), + (Tuple(Ge(a, b), Gt(b, c), Gt(c, a)), false), + (Tuple(Gt(a, b), Gt(b, c), Gt(c, a)), false), + # (Tuple(Ge(c, a), Gt(a, b), Gt(b, c)), S.false), + # Lower bound relations + # Commented out combinations that does not simplify + (Tuple(Ge(a, b), Ge(a, c), Ge(b, c)), And(Ge(a, b), Ge(b, c))), + (Tuple(Ge(a, b), Ge(a, c), Gt(b, c)), And(Ge(a, b), Gt(b, c))), + # (Tuple(Ge(a, b), Gt(a, c), Ge(b, c)), And(Ge(a, b), Ge(b, c))), + (Tuple(Ge(a, b), Gt(a, c), Gt(b, c)), And(Ge(a, b), Gt(b, c))), + # (Tuple(Gt(a, b), Ge(a, c), Ge(b, c)), And(Gt(a, b), Ge(b, c))), + (Tuple(Ge(a, c), Gt(a, b), Gt(b, c)), And(Gt(a, b), Gt(b, c))), + (Tuple(Ge(b, c), Gt(a, b), Gt(a, c)), And(Gt(a, b), Ge(b, c))), + (Tuple(Gt(a, b), Gt(a, c), Gt(b, c)), And(Gt(a, b), Gt(b, c))), + # Upper bound relations + # Commented out combinations that does not simplify + (Tuple(Ge(b, a), Ge(c, a), Ge(b, c)), And(Ge(c, a), Ge(b, c))), + (Tuple(Ge(b, a), Ge(c, a), Gt(b, c)), And(Ge(c, a), Gt(b, c))), + # (Tuple(Ge(b, a), Gt(c, a), Ge(b, c)), And(Gt(c, a), Ge(b, c))), + (Tuple(Ge(b, a), Gt(c, a), Gt(b, c)), And(Gt(c, a), Gt(b, c))), + # (Tuple(Gt(b, a), Ge(c, a), Ge(b, c)), And(Ge(c, a), Ge(b, c))), + (Tuple(Ge(c, a), Gt(b, a), Gt(b, c)), And(Ge(c, a), Gt(b, c))), + (Tuple(Ge(b, c), Gt(b, a), Gt(c, a)), And(Gt(c, a), Ge(b, c))), + (Tuple(Gt(b, a), Gt(c, a), Gt(b, c)), And(Gt(c, a), Gt(b, c))), + # Circular relation + (Tuple(Ge(a, b), Ge(b, c), Ge(c, a)), And(Eq(a, b), Eq(b, c))), + ) + return _matchers_and + + +@cacheit +def _simplify_patterns_or(): + """ Two-term patterns for Or.""" + + from sympy.core import Wild + from sympy.core.relational import Eq, Ne, Ge, Gt, Le, Lt + from sympy.functions.elementary.complexes import Abs + from sympy.functions.elementary.miscellaneous import Min, Max + a = Wild('a') + b = Wild('b') + c = Wild('c') + # Relationals patterns should be in alphabetical order + # (pattern1, pattern2, simplified) + # Do not use Ge, Gt + _matchers_or = ((Tuple(Le(b, a), Le(a, b)), true), + #(Tuple(Le(b, a), Lt(a, b)), true), + (Tuple(Le(b, a), Ne(a, b)), true), + #(Tuple(Le(a, b), Lt(b, a)), true), + #(Tuple(Le(a, b), Ne(a, b)), true), + #(Tuple(Eq(a, b), Le(b, a)), Ge(a, b)), + #(Tuple(Eq(a, b), Lt(b, a)), Ge(a, b)), + (Tuple(Eq(a, b), Le(a, b)), Le(a, b)), + (Tuple(Eq(a, b), Lt(a, b)), Le(a, b)), + #(Tuple(Le(b, a), Lt(b, a)), Ge(a, b)), + (Tuple(Lt(b, a), Lt(a, b)), Ne(a, b)), + (Tuple(Lt(b, a), Ne(a, b)), Ne(a, b)), + (Tuple(Le(a, b), Lt(a, b)), Le(a, b)), + #(Tuple(Lt(a, b), Ne(a, b)), Ne(a, b)), + (Tuple(Eq(a, b), Ne(a, c)), ITE(Eq(b, c), true, Ne(a, c))), + (Tuple(Ne(a, b), Ne(a, c)), ITE(Eq(b, c), Ne(a, b), true)), + # Min/Max/ITE + (Tuple(Le(b, a), Le(c, a)), Ge(a, Min(b, c))), + #(Tuple(Ge(b, a), Ge(c, a)), Ge(Min(b, c), a)), + (Tuple(Le(b, a), Lt(c, a)), ITE(b > c, Lt(c, a), Le(b, a))), + (Tuple(Lt(b, a), Lt(c, a)), Gt(a, Min(b, c))), + #(Tuple(Gt(b, a), Gt(c, a)), Gt(Min(b, c), a)), + (Tuple(Le(a, b), Le(a, c)), Le(a, Max(b, c))), + #(Tuple(Le(b, a), Le(c, a)), Le(Max(b, c), a)), + (Tuple(Le(a, b), Lt(a, c)), ITE(b >= c, Le(a, b), Lt(a, c))), + (Tuple(Lt(a, b), Lt(a, c)), Lt(a, Max(b, c))), + #(Tuple(Lt(b, a), Lt(c, a)), Lt(Max(b, c), a)), + (Tuple(Le(a, b), Le(c, a)), ITE(b >= c, true, Or(Le(a, b), Ge(a, c)))), + (Tuple(Le(c, a), Le(a, b)), ITE(b >= c, true, Or(Le(a, b), Ge(a, c)))), + (Tuple(Lt(a, b), Lt(c, a)), ITE(b > c, true, Or(Lt(a, b), Gt(a, c)))), + (Tuple(Lt(c, a), Lt(a, b)), ITE(b > c, true, Or(Lt(a, b), Gt(a, c)))), + (Tuple(Le(a, b), Lt(c, a)), ITE(b >= c, true, Or(Le(a, b), Gt(a, c)))), + (Tuple(Le(c, a), Lt(a, b)), ITE(b >= c, true, Or(Lt(a, b), Ge(a, c)))), + (Tuple(Lt(b, a), Lt(a, -b)), ITE(b >= 0, Gt(Abs(a), b), true)), + (Tuple(Le(b, a), Le(a, -b)), ITE(b > 0, Ge(Abs(a), b), true)), + ) + return _matchers_or + + +@cacheit +def _simplify_patterns_xor(): + """ Two-term patterns for Xor.""" + + from sympy.functions.elementary.miscellaneous import Min, Max + from sympy.core import Wild + from sympy.core.relational import Eq, Ne, Ge, Gt, Le, Lt + a = Wild('a') + b = Wild('b') + c = Wild('c') + # Relationals patterns should be in alphabetical order + # (pattern1, pattern2, simplified) + # Do not use Ge, Gt + _matchers_xor = (#(Tuple(Le(b, a), Lt(a, b)), true), + #(Tuple(Lt(b, a), Le(a, b)), true), + #(Tuple(Eq(a, b), Le(b, a)), Gt(a, b)), + #(Tuple(Eq(a, b), Lt(b, a)), Ge(a, b)), + (Tuple(Eq(a, b), Le(a, b)), Lt(a, b)), + (Tuple(Eq(a, b), Lt(a, b)), Le(a, b)), + (Tuple(Le(a, b), Lt(a, b)), Eq(a, b)), + (Tuple(Le(a, b), Le(b, a)), Ne(a, b)), + (Tuple(Le(b, a), Ne(a, b)), Le(a, b)), + # (Tuple(Lt(b, a), Lt(a, b)), Ne(a, b)), + (Tuple(Lt(b, a), Ne(a, b)), Lt(a, b)), + # (Tuple(Le(a, b), Lt(a, b)), Eq(a, b)), + # (Tuple(Le(a, b), Ne(a, b)), Ge(a, b)), + # (Tuple(Lt(a, b), Ne(a, b)), Gt(a, b)), + # Min/Max/ITE + (Tuple(Le(b, a), Le(c, a)), + And(Ge(a, Min(b, c)), Lt(a, Max(b, c)))), + (Tuple(Le(b, a), Lt(c, a)), + ITE(b > c, And(Gt(a, c), Lt(a, b)), + And(Ge(a, b), Le(a, c)))), + (Tuple(Lt(b, a), Lt(c, a)), + And(Gt(a, Min(b, c)), Le(a, Max(b, c)))), + (Tuple(Le(a, b), Le(a, c)), + And(Le(a, Max(b, c)), Gt(a, Min(b, c)))), + (Tuple(Le(a, b), Lt(a, c)), + ITE(b < c, And(Lt(a, c), Gt(a, b)), + And(Le(a, b), Ge(a, c)))), + (Tuple(Lt(a, b), Lt(a, c)), + And(Lt(a, Max(b, c)), Ge(a, Min(b, c)))), + ) + return _matchers_xor + + +def simplify_univariate(expr): + """return a simplified version of univariate boolean expression, else ``expr``""" + from sympy.functions.elementary.piecewise import Piecewise + from sympy.core.relational import Eq, Ne + if not isinstance(expr, BooleanFunction): + return expr + if expr.atoms(Eq, Ne): + return expr + c = expr + free = c.free_symbols + if len(free) != 1: + return c + x = free.pop() + ok, i = Piecewise((0, c), evaluate=False + )._intervals(x, err_on_Eq=True) + if not ok: + return c + if not i: + return false + args = [] + for a, b, _, _ in i: + if a is S.NegativeInfinity: + if b is S.Infinity: + c = true + else: + if c.subs(x, b) == True: + c = (x <= b) + else: + c = (x < b) + else: + incl_a = (c.subs(x, a) == True) + incl_b = (c.subs(x, b) == True) + if incl_a and incl_b: + if b.is_infinite: + c = (x >= a) + else: + c = And(a <= x, x <= b) + elif incl_a: + c = And(a <= x, x < b) + elif incl_b: + if b.is_infinite: + c = (x > a) + else: + c = And(a < x, x <= b) + else: + c = And(a < x, x < b) + args.append(c) + return Or(*args) + + +# Classes corresponding to logic gates +# Used in gateinputcount method +BooleanGates = (And, Or, Xor, Nand, Nor, Not, Xnor, ITE) + +def gateinputcount(expr): + """ + Return the total number of inputs for the logic gates realizing the + Boolean expression. + + Returns + ======= + + int + Number of gate inputs + + Note + ==== + + Not all Boolean functions count as gate here, only those that are + considered to be standard gates. These are: :py:class:`~.And`, + :py:class:`~.Or`, :py:class:`~.Xor`, :py:class:`~.Not`, and + :py:class:`~.ITE` (multiplexer). :py:class:`~.Nand`, :py:class:`~.Nor`, + and :py:class:`~.Xnor` will be evaluated to ``Not(And())`` etc. + + Examples + ======== + + >>> from sympy.logic import And, Or, Nand, Not, gateinputcount + >>> from sympy.abc import x, y, z + >>> expr = And(x, y) + >>> gateinputcount(expr) + 2 + >>> gateinputcount(Or(expr, z)) + 4 + + Note that ``Nand`` is automatically evaluated to ``Not(And())`` so + + >>> gateinputcount(Nand(x, y, z)) + 4 + >>> gateinputcount(Not(And(x, y, z))) + 4 + + Although this can be avoided by using ``evaluate=False`` + + >>> gateinputcount(Nand(x, y, z, evaluate=False)) + 3 + + Also note that a comparison will count as a Boolean variable: + + >>> gateinputcount(And(x > z, y >= 2)) + 2 + + As will a symbol: + >>> gateinputcount(x) + 0 + + """ + if not isinstance(expr, Boolean): + raise TypeError("Expression must be Boolean") + if isinstance(expr, BooleanGates): + return len(expr.args) + sum(gateinputcount(x) for x in expr.args) + return 0