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Small implementation improvement in linexprs.py
[linpy.git] / pypol / linexprs.py
diff --git a/pypol/linexprs.py b/pypol/linexprs.py
index b23eea8..c5f4336 100644 (file)
--- a/pypol/linexprs.py
+++ b/pypol/linexprs.py
@@ -31,47 +31,35 @@ class Expression:
     This class implements linear expressions.
     """
 
     This class implements linear expressions.
     """
 
-    __slots__ = (
-        '_coefficients',
-        '_constant',
-        '_symbols',
-        '_dimension',
-    )
-
     def __new__(cls, coefficients=None, constant=0):
         if isinstance(coefficients, str):
     def __new__(cls, coefficients=None, constant=0):
         if isinstance(coefficients, str):
-            if constant:
+            if constant != 0:
                 raise TypeError('too many arguments')
             return Expression.fromstring(coefficients)
         if coefficients is None:
             return Rational(constant)
         if isinstance(coefficients, Mapping):
             coefficients = coefficients.items()
                 raise TypeError('too many arguments')
             return Expression.fromstring(coefficients)
         if coefficients is None:
             return Rational(constant)
         if isinstance(coefficients, Mapping):
             coefficients = coefficients.items()
+        coefficients = list(coefficients)
         for symbol, coefficient in coefficients:
             if not isinstance(symbol, Symbol):
                 raise TypeError('symbols must be Symbol instances')
         for symbol, coefficient in coefficients:
             if not isinstance(symbol, Symbol):
                 raise TypeError('symbols must be Symbol instances')
-        coefficients = [(symbol, coefficient)
-            for symbol, coefficient in coefficients if coefficient != 0]
+            if not isinstance(coefficient, numbers.Rational):
+                raise TypeError('coefficients must be rational numbers')
+        if not isinstance(constant, numbers.Rational):
+            raise TypeError('constant must be a rational number')
         if len(coefficients) == 0:
             return Rational(constant)
         if len(coefficients) == 1 and constant == 0:
             symbol, coefficient = coefficients[0]
             if coefficient == 1:
                 return symbol
         if len(coefficients) == 0:
             return Rational(constant)
         if len(coefficients) == 1 and constant == 0:
             symbol, coefficient = coefficients[0]
             if coefficient == 1:
                 return symbol
+        coefficients = [(symbol, Fraction(coefficient))
+            for symbol, coefficient in coefficients if coefficient != 0]
+        coefficients.sort(key=lambda item: item[0].sortkey())
         self = object().__new__(cls)
         self = object().__new__(cls)
-        self._coefficients = OrderedDict()
-        for symbol, coefficient in sorted(coefficients,
-                key=lambda item: item[0].sortkey()):
-            if isinstance(coefficient, Rational):
-                coefficient = coefficient.constant
-            if not isinstance(coefficient, numbers.Rational):
-                raise TypeError('coefficients must be Rational instances')
-            self._coefficients[symbol] = coefficient
-        if isinstance(constant, Rational):
-            constant = constant.constant
-        if not isinstance(constant, numbers.Rational):
-            raise TypeError('constant must be a Rational instance')
-        self._constant = constant
+        self._coefficients = OrderedDict(coefficients)
+        self._constant = Fraction(constant)
         self._symbols = tuple(self._coefficients)
         self._dimension = len(self._symbols)
         return self
         self._symbols = tuple(self._coefficients)
         self._dimension = len(self._symbols)
         return self
@@ -79,19 +67,17 @@ class Expression:
     def coefficient(self, symbol):
         if not isinstance(symbol, Symbol):
             raise TypeError('symbol must be a Symbol instance')
     def coefficient(self, symbol):
         if not isinstance(symbol, Symbol):
             raise TypeError('symbol must be a Symbol instance')
-        try:
-            return self._coefficients[symbol]
-        except KeyError:
-            return 0
+        return Rational(self._coefficients.get(symbol, 0))
 
     __getitem__ = coefficient
 
     def coefficients(self):
 
     __getitem__ = coefficient
 
     def coefficients(self):
-        yield from self._coefficients.items()
+        for symbol, coefficient in self._coefficients.items():
+            yield symbol, Rational(coefficient)
 
     @property
     def constant(self):
 
     @property
     def constant(self):
-        return self._constant
+        return Rational(self._constant)
 
     @property
     def symbols(self):
 
     @property
     def symbols(self):
@@ -111,8 +97,9 @@ class Expression:
         return False
 
     def values(self):
         return False
 
     def values(self):
-        yield from self._coefficients.values()
-        yield self.constant
+        for coefficient in self._coefficients.values():
+            yield Rational(coefficient)
+        yield Rational(self._constant)
 
     def __bool__(self):
         return True
 
     def __bool__(self):
         return True
@@ -125,86 +112,64 @@ class Expression:
 
     @_polymorphic
     def __add__(self, other):
 
     @_polymorphic
     def __add__(self, other):
-        coefficients = defaultdict(Rational, self.coefficients())
-        for symbol, coefficient in other.coefficients():
+        coefficients = defaultdict(Fraction, self._coefficients)
+        for symbol, coefficient in other._coefficients.items():
             coefficients[symbol] += coefficient
             coefficients[symbol] += coefficient
-        constant = self.constant + other.constant
+        constant = self._constant + other._constant
         return Expression(coefficients, constant)
 
     __radd__ = __add__
 
     @_polymorphic
     def __sub__(self, other):
         return Expression(coefficients, constant)
 
     __radd__ = __add__
 
     @_polymorphic
     def __sub__(self, other):
-        coefficients = defaultdict(Rational, self.coefficients())
-        for symbol, coefficient in other.coefficients():
+        coefficients = defaultdict(Fraction, self._coefficients)
+        for symbol, coefficient in other._coefficients.items():
             coefficients[symbol] -= coefficient
             coefficients[symbol] -= coefficient
-        constant = self.constant - other.constant
+        constant = self._constant - other._constant
         return Expression(coefficients, constant)
 
         return Expression(coefficients, constant)
 
+    @_polymorphic
     def __rsub__(self, other):
     def __rsub__(self, other):
-        return -(self - other)
+        return other - self
 
 
-    @_polymorphic
     def __mul__(self, other):
     def __mul__(self, other):
-        if other.isconstant():
-            coefficients = dict(self.coefficients())
-            for symbol in coefficients:
-                coefficients[symbol] *= other.constant
-            constant = self.constant * other.constant
+        if isinstance(other, numbers.Rational):
+            coefficients = ((symbol, coefficient * other)
+                for symbol, coefficient in self._coefficients.items())
+            constant = self._constant * other
             return Expression(coefficients, constant)
             return Expression(coefficients, constant)
-        if isinstance(other, Expression) and not self.isconstant():
-            raise ValueError('non-linear expression: '
-                    '{} * {}'.format(self._parenstr(), other._parenstr()))
         return NotImplemented
 
     __rmul__ = __mul__
 
         return NotImplemented
 
     __rmul__ = __mul__
 
-    @_polymorphic
     def __truediv__(self, other):
     def __truediv__(self, other):
-        if other.isconstant():
-            coefficients = dict(self.coefficients())
-            for symbol in coefficients:
-                coefficients[symbol] = Rational(coefficients[symbol], other.constant)
-            constant = Rational(self.constant, other.constant)
+        if isinstance(other, numbers.Rational):
+            coefficients = ((symbol, coefficient / other)
+                for symbol, coefficient in self._coefficients.items())
+            constant = self._constant / other
             return Expression(coefficients, constant)
             return Expression(coefficients, constant)
-        if isinstance(other, Expression):
-            raise ValueError('non-linear expression: '
-                '{} / {}'.format(self._parenstr(), other._parenstr()))
-        return NotImplemented
-
-    def __rtruediv__(self, other):
-        if isinstance(other, self):
-            if self.isconstant():
-                return Rational(other, self.constant)
-            else:
-                raise ValueError('non-linear expression: '
-                        '{} / {}'.format(other._parenstr(), self._parenstr()))
         return NotImplemented
 
     @_polymorphic
     def __eq__(self, other):
         return NotImplemented
 
     @_polymorphic
     def __eq__(self, other):
-        # "normal" equality
+        # returns a boolean, not a constraint
         # see http://docs.sympy.org/dev/tutorial/gotchas.html#equals-signs
         return isinstance(other, Expression) and \
             self._coefficients == other._coefficients and \
         # see http://docs.sympy.org/dev/tutorial/gotchas.html#equals-signs
         return isinstance(other, Expression) and \
             self._coefficients == other._coefficients and \
-            self.constant == other.constant
+            self._constant == other._constant
 
 
-    @_polymorphic
     def __le__(self, other):
         from .polyhedra import Le
         return Le(self, other)
 
     def __le__(self, other):
         from .polyhedra import Le
         return Le(self, other)
 
-    @_polymorphic
     def __lt__(self, other):
         from .polyhedra import Lt
         return Lt(self, other)
 
     def __lt__(self, other):
         from .polyhedra import Lt
         return Lt(self, other)
 
-    @_polymorphic
     def __ge__(self, other):
         from .polyhedra import Ge
         return Ge(self, other)
 
     def __ge__(self, other):
         from .polyhedra import Ge
         return Ge(self, other)
 
-    @_polymorphic
     def __gt__(self, other):
         from .polyhedra import Gt
         return Gt(self, other)
     def __gt__(self, other):
         from .polyhedra import Gt
         return Gt(self, other)
@@ -223,11 +188,13 @@ class Expression:
             substitutions = [(symbol, expression)]
         result = self
         for symbol, expression in substitutions:
             substitutions = [(symbol, expression)]
         result = self
         for symbol, expression in substitutions:
+            if not isinstance(symbol, Symbol):
+                raise TypeError('symbols must be Symbol instances')
             coefficients = [(othersymbol, coefficient)
             coefficients = [(othersymbol, coefficient)
-                for othersymbol, coefficient in result.coefficients()
+                for othersymbol, coefficient in result._coefficients.items()
                 if othersymbol != symbol]
                 if othersymbol != symbol]
-            coefficient = result.coefficient(symbol)
-            constant = result.constant
+            coefficient = result._coefficients.get(symbol, 0)
+            constant = result._constant
             result = Expression(coefficients, constant) + coefficient*expression
         return result
 
             result = Expression(coefficients, constant) + coefficient*expression
         return result
 
@@ -269,18 +236,17 @@ class Expression:
         string = ''
         for i, (symbol, coefficient) in enumerate(self.coefficients()):
             if coefficient == 1:
         string = ''
         for i, (symbol, coefficient) in enumerate(self.coefficients()):
             if coefficient == 1:
-                string += '' if i == 0 else ' + '
-                string += '{!r}'.format(symbol)
+                if i != 0:
+                    string += ' + '
             elif coefficient == -1:
                 string += '-' if i == 0 else ' - '
             elif coefficient == -1:
                 string += '-' if i == 0 else ' - '
-                string += '{!r}'.format(symbol)
+            elif i == 0:
+                string += '{}*'.format(coefficient)
+            elif coefficient > 0:
+                string += ' + {}*'.format(coefficient)
             else:
             else:
-                if i == 0:
-                    string += '{}*{!r}'.format(coefficient, symbol)
-                elif coefficient > 0:
-                    string += ' + {}*{!r}'.format(coefficient, symbol)
-                else:
-                    string += ' - {}*{!r}'.format(-coefficient, symbol)
+                string += ' - {}*'.format(-coefficient)
+            string += '{}'.format(symbol)
         constant = self.constant
         if len(string) == 0:
             string += '{}'.format(constant)
         constant = self.constant
         if len(string) == 0:
             string += '{}'.format(constant)
@@ -290,6 +256,30 @@ class Expression:
             string += ' - {}'.format(-constant)
         return string
 
             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()):
     def _parenstr(self, always=False):
         string = str(self)
         if not always and (self.isconstant() or self.issymbol()):
@@ -325,15 +315,15 @@ class Expression:
 
 class Symbol(Expression):
 
 
 class Symbol(Expression):
 
-    __slots__ = (
-        '_name',
-    )
-
     def __new__(cls, name):
         if not isinstance(name, str):
             raise TypeError('name must be a string')
         self = object().__new__(cls)
         self._name = name.strip()
     def __new__(cls, name):
         if not isinstance(name, str):
             raise TypeError('name must be a string')
         self = object().__new__(cls)
         self._name = name.strip()
+        self._coefficients = {self: Fraction(1)}
+        self._constant = Fraction(0)
+        self._symbols = (self,)
+        self._dimension = 1
         return self
 
     @property
         return self
 
     @property
@@ -343,41 +333,14 @@ class Symbol(Expression):
     def __hash__(self):
         return hash(self.sortkey())
 
     def __hash__(self):
         return hash(self.sortkey())
 
-    def coefficient(self, symbol):
-        if not isinstance(symbol, Symbol):
-            raise TypeError('symbol must be a Symbol instance')
-        if symbol == self:
-            return 1
-        else:
-            return 0
-
-    def coefficients(self):
-        yield self, 1
-
-    @property
-    def constant(self):
-        return 0
-
-    @property
-    def symbols(self):
-        return self,
-
-    @property
-    def dimension(self):
-        return 1
-
     def sortkey(self):
         return self.name,
 
     def issymbol(self):
         return True
 
     def sortkey(self):
         return self.name,
 
     def issymbol(self):
         return True
 
-    def values(self):
-        yield 1
-
     def __eq__(self, other):
     def __eq__(self, other):
-        return not isinstance(other, Dummy) and isinstance(other, Symbol) \
-            and self.name == other.name
+        return self.sortkey() == other.sortkey()
 
     def asdummy(self):
         return Dummy(self.name)
 
     def asdummy(self):
         return Dummy(self.name)
@@ -395,30 +358,36 @@ class Symbol(Expression):
     def __repr__(self):
         return self.name
 
     def __repr__(self):
         return self.name
 
+    def _repr_latex_(self):
+        return '${}$'.format(self.name)
+
     @classmethod
     def fromsympy(cls, expr):
         import sympy
     @classmethod
     def fromsympy(cls, expr):
         import sympy
-        if isinstance(expr, sympy.Symbol):
-            return cls(expr.name)
+        if isinstance(expr, sympy.Dummy):
+            return Dummy(expr.name)
+        elif isinstance(expr, sympy.Symbol):
+            return Symbol(expr.name)
         else:
             raise TypeError('expr must be a sympy.Symbol instance')
 
 
 class Dummy(Symbol):
 
         else:
             raise TypeError('expr must be a sympy.Symbol instance')
 
 
 class Dummy(Symbol):
 
-    __slots__ = (
-        '_name',
-        '_index',
-    )
-
     _count = 0
 
     def __new__(cls, name=None):
         if name is None:
             name = 'Dummy_{}'.format(Dummy._count)
     _count = 0
 
     def __new__(cls, name=None):
         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 = object().__new__(cls)
-        self._name = name.strip()
         self._index = Dummy._count
         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
 
         Dummy._count += 1
         return self
 
@@ -428,12 +397,12 @@ class Dummy(Symbol):
     def sortkey(self):
         return self._name, self._index
 
     def sortkey(self):
         return self._name, self._index
 
-    def __eq__(self, other):
-        return isinstance(other, Dummy) and self._index == other._index
-
     def __repr__(self):
         return '_{}'.format(self.name)
 
     def __repr__(self):
         return '_{}'.format(self.name)
 
+    def _repr_latex_(self):
+        return '${}_{{{}}}$'.format(self.name, self._index)
+
 
 def symbols(names):
     if isinstance(names, str):
 
 def symbols(names):
     if isinstance(names, str):
@@ -441,57 +410,44 @@ def symbols(names):
     return tuple(Symbol(name) for name in names)
 
 
     return tuple(Symbol(name) for name in names)
 
 
-class Rational(Expression):
-
-    __slots__ = (
-        '_constant',
-    )
+class Rational(Expression, Fraction):
 
     def __new__(cls, numerator=0, denominator=None):
 
     def __new__(cls, numerator=0, denominator=None):
-        self = object().__new__(cls)
-        if denominator is None and isinstance(numerator, Rational):
-            self._constant = numerator.constant
-        else:
-            self._constant = Fraction(numerator, denominator)
+        self = Fraction.__new__(cls, numerator, denominator)
+        self._coefficients = {}
+        self._constant = Fraction(self)
+        self._symbols = ()
+        self._dimension = 0
         return self
 
     def __hash__(self):
         return self
 
     def __hash__(self):
-        return hash(self.constant)
-
-    def coefficient(self, symbol):
-        if not isinstance(symbol, Symbol):
-            raise TypeError('symbol must be a Symbol instance')
-        return 0
-
-    def coefficients(self):
-        yield from ()
-
-    @property
-    def symbols(self):
-        return ()
+        return Fraction.__hash__(self)
 
     @property
 
     @property
-    def dimension(self):
-        return 0
+    def constant(self):
+        return self
 
     def isconstant(self):
         return True
 
 
     def isconstant(self):
         return True
 
-    def values(self):
-        yield self._constant
-
-    @_polymorphic
-    def __eq__(self, other):
-        return isinstance(other, Rational) and self.constant == other.constant
-
     def __bool__(self):
     def __bool__(self):
-        return self.constant != 0
+        return Fraction.__bool__(self)
 
 
-    @classmethod
-    def fromstring(cls, string):
-        if not isinstance(string, str):
-            raise TypeError('string must be a string instance')
-        return Rational(Fraction(string))
+    def __repr__(self):
+        if self.denominator == 1:
+            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)
 
     @classmethod
     def fromsympy(cls, expr):
 
     @classmethod
     def fromsympy(cls, expr):
A polyhedral library based on ISL