X-Git-Url: https://scm.cri.ensmp.fr/git/linpy.git/blobdiff_plain/7fda4e3865bb7cc9b6ee15cfd3c62c207f585ec7..1044e58e639333d281d47739ba9ecef607ff14e6:/linpy/linexprs.py diff --git a/linpy/linexprs.py b/linpy/linexprs.py index b5864e1..f361218 100644 --- a/linpy/linexprs.py +++ b/linpy/linexprs.py @@ -62,7 +62,7 @@ class LinExpr: symbols to their coefficients, and a constant term. The coefficients and the constant term must be rational numbers. - For example, the linear expression x + 2y + 1 can be constructed using + For example, the linear expression x + 2*y + 1 can be constructed using one of the following instructions: >>> x, y = symbols('x y') @@ -76,7 +76,7 @@ class LinExpr: Alternatively, linear expressions can be constructed from a string: - >>> LinExpr('x + 2*y + 1') + >>> LinExpr('x + 2y + 1') A linear expression with a single symbol of coefficient 1 and no constant term is automatically subclassed as a Symbol instance. A linear @@ -245,28 +245,34 @@ class LinExpr: @_polymorphic def __eq__(self, other): """ - Test whether two linear expressions are equal. + Test whether two linear expressions are equal. Unlike methods + LinExpr.__lt__(), LinExpr.__le__(), LinExpr.__ge__(), LinExpr.__gt__(), + the result is a boolean value, not a polyhedron. To express that two + linear expressions are equal or not equal, use functions Eq() and Ne() + instead. """ - if isinstance(other, LinExpr): - return self._coefficients == other._coefficients and \ - self._constant == other._constant - return NotImplemented - - def __le__(self, other): - from .polyhedra import Le - return Le(self, other) + return self._coefficients == other._coefficients and \ + self._constant == other._constant + @_polymorphic def __lt__(self, other): - from .polyhedra import Lt - return Lt(self, other) + from .polyhedra import Polyhedron + return Polyhedron([], [other - self - 1]) + + @_polymorphic + def __le__(self, other): + from .polyhedra import Polyhedron + return Polyhedron([], [other - self]) + @_polymorphic def __ge__(self, other): - from .polyhedra import Ge - return Ge(self, other) + from .polyhedra import Polyhedron + return Polyhedron([], [self - other]) + @_polymorphic def __gt__(self, other): - from .polyhedra import Gt - return Gt(self, other) + from .polyhedra import Polyhedron + return Polyhedron([], [self - other - 1]) def scaleint(self): """ @@ -300,7 +306,7 @@ class LinExpr: for symbol in substitutions: if not isinstance(symbol, Symbol): raise TypeError('symbols must be Symbol instances') - result = self._constant + result = Rational(self._constant) for symbol, coefficient in self._coefficients.items(): expression = substitutions.get(symbol, symbol) result += coefficient * expression @@ -331,7 +337,7 @@ class LinExpr: return left / right raise SyntaxError('invalid syntax') - _RE_NUM_VAR = re.compile(r'(\d+|\))\s*([^\W\d_]\w*|$$)') + _RE_NUM_VAR = re.compile(r'(\d+|$$)\s*([^\W\d]\w*|\()') @classmethod def fromstring(cls, string): @@ -339,13 +345,13 @@ class LinExpr: Create an expression from a string. Raise SyntaxError if the string is not properly formatted. """ - # add implicit multiplication operators, e.g. '5x' -> '5*x' + # Add implicit multiplication operators, e.g. '5x' -> '5*x'. string = LinExpr._RE_NUM_VAR.sub(r'\1*\2', string) tree = ast.parse(string, 'eval') - expr = cls._fromast(tree) - if not isinstance(expr, cls): + expression = cls._fromast(tree) + if not isinstance(expression, cls): raise SyntaxError('invalid syntax') - return expr + return expression def __repr__(self): string = '' @@ -371,30 +377,6 @@ class LinExpr: string += ' - {}'.format(-constant) return string - def _repr_latex_(self): - string = '' - for i, (symbol, coefficient) in enumerate(self.coefficients()): - if coefficient == 1: - if i != 0: - string += ' + ' - elif coefficient == -1: - string += '-' if i == 0 else ' - ' - elif i == 0: - string += '{}'.format(coefficient._repr_latex_().strip('$')) - elif coefficient > 0: - string += ' + {}'.format(coefficient._repr_latex_().strip('$')) - elif coefficient < 0: - string += ' - {}'.format((-coefficient)._repr_latex_().strip('$')) - string += '{}'.format(symbol._repr_latex_().strip('$')) - constant = self.constant - if len(string) == 0: - string += '{}'.format(constant._repr_latex_().strip('$')) - elif constant > 0: - string += ' + {}'.format(constant._repr_latex_().strip('$')) - elif constant < 0: - string += ' - {}'.format((-constant)._repr_latex_().strip('\$')) - return '$${}$$'.format(string) - def _parenstr(self, always=False): string = str(self) if not always and (self.isconstant() or self.issymbol()): @@ -403,42 +385,43 @@ class LinExpr: return '({})'.format(string) @classmethod - def fromsympy(cls, expr): + def fromsympy(cls, expression): """ - Create a linear expression from a sympy expression. Raise TypeError is + Create a linear expression from a SymPy expression. Raise TypeError is the sympy expression is not linear. """ import sympy coefficients = [] constant = 0 - for symbol, coefficient in expr.as_coefficients_dict().items(): + for symbol, coefficient in expression.as_coefficients_dict().items(): coefficient = Fraction(coefficient.p, coefficient.q) if symbol == sympy.S.One: constant = coefficient elif isinstance(symbol, sympy.Dummy): - # we cannot properly convert dummy symbols + # We cannot properly convert dummy symbols with respect to + # symbol equalities. raise TypeError('cannot convert dummy symbols') elif isinstance(symbol, sympy.Symbol): symbol = Symbol(symbol.name) coefficients.append((symbol, coefficient)) else: - raise TypeError('non-linear expression: {!r}'.format(expr)) - expr = LinExpr(coefficients, constant) - if not isinstance(expr, cls): + raise TypeError('non-linear expression: {!r}'.format(expression)) + expression = LinExpr(coefficients, constant) + if not isinstance(expression, cls): raise TypeError('cannot convert to a {} instance'.format(cls.__name__)) - return expr + return expression def tosympy(self): """ - Convert the linear expression to a sympy expression. + Convert the linear expression to a SymPy expression. """ import sympy - expr = 0 + expression = 0 for symbol, coefficient in self.coefficients(): term = coefficient * sympy.Symbol(symbol.name) - expr += term - expr += self.constant - return expr + expression += term + expression += self.constant + return expression class Symbol(LinExpr): @@ -450,6 +433,13 @@ class Symbol(LinExpr): Two instances of Symbol are equal if they have the same name. """ + __slots__ = ( + '_name', + '_constant', + '_symbols', + '_dimension', + ) + def __new__(cls, name): """ Return a symbol with the name string given in argument. @@ -463,12 +453,17 @@ class Symbol(LinExpr): raise SyntaxError('invalid syntax') self = object().__new__(cls) self._name = name - self._coefficients = {self: Fraction(1)} self._constant = Fraction(0) self._symbols = (self,) self._dimension = 1 return self + @property + def _coefficients(self): + # This is not implemented as an attribute, because __hash__ is not + # callable in __new__ in class Dummy. + return {self: Fraction(1)} + @property def name(self): """ @@ -506,9 +501,6 @@ class Symbol(LinExpr): def __repr__(self): return self.name - def _repr_latex_(self): - return '$${}$$'.format(self.name) - def symbols(names): """ @@ -553,15 +545,8 @@ class Dummy(Symbol): """ if name is None: name = 'Dummy_{}'.format(Dummy._count) - elif not isinstance(name, str): - raise TypeError('name must be a string') - self = object().__new__(cls) + self = super().__new__(cls, name) self._index = Dummy._count - self._name = name.strip() - self._coefficients = {self: Fraction(1)} - self._constant = Fraction(0) - self._symbols = (self,) - self._dimension = 1 Dummy._count += 1 return self @@ -574,9 +559,6 @@ class Dummy(Symbol): def __repr__(self): return '_{}'.format(self.name) - def _repr_latex_(self): - return '$${}_{{{}}}$$'.format(self.name, self._index) - class Rational(LinExpr, Fraction): """ @@ -586,6 +568,13 @@ class Rational(LinExpr, Fraction): fractions.Fraction classes. """ + __slots__ = ( + '_coefficients', + '_constant', + '_symbols', + '_dimension', + ) + Fraction.__slots__ + def __new__(cls, numerator=0, denominator=None): self = object().__new__(cls) self._coefficients = {} @@ -614,13 +603,3 @@ class Rational(LinExpr, Fraction): return '{!r}'.format(self.numerator) else: return '{!r}/{!r}'.format(self.numerator, self.denominator) - - def _repr_latex_(self): - if self.denominator == 1: - return '$${}$$'.format(self.numerator) - elif self.numerator < 0: - return '$$-\\frac{{{}}}{{{}}}$$'.format(-self.numerator, - self.denominator) - else: - return '$$\\frac{{{}}}{{{}}}$$'.format(self.numerator, - self.denominator)