Cleaner implementation of Rational

diff --git a/pypol/linexprs.py b/pypol/linexprs.py
index b23eea8..e73449e 100644 (file)
--- a/pypol/linexprs.py
+++ b/pypol/linexprs.py
@@ -31,16 +31,9 @@ class Expression:
     This class implements linear expressions.
     """
 
-    __slots__ = (
-        '_coefficients',
-        '_constant',
-        '_symbols',
-        '_dimension',
-    )
-
     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:
@@ -50,8 +43,13 @@ class Expression:
         for symbol, coefficient in coefficients:
             if not isinstance(symbol, Symbol):
                 raise TypeError('symbols must be Symbol instances')
-        coefficients = [(symbol, coefficient)
+            if not isinstance(coefficient, numbers.Rational):
+                raise TypeError('coefficients must be Rational instances')
+        coefficients = [(symbol, Fraction(coefficient))
             for symbol, coefficient in coefficients if coefficient != 0]
+        if not isinstance(constant, numbers.Rational):
+            raise TypeError('constant must be a Rational instance')
+        constant = Fraction(constant)
         if len(coefficients) == 0:
             return Rational(constant)
         if len(coefficients) == 1 and constant == 0:
@@ -59,18 +57,8 @@ class Expression:
             if coefficient == 1:
                 return symbol
         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._coefficients = OrderedDict(sorted(coefficients,
+            key=lambda item: item[0].sortkey()))
         self._constant = constant
         self._symbols = tuple(self._coefficients)
         self._dimension = len(self._symbols)
@@ -80,18 +68,19 @@ class Expression:
         if not isinstance(symbol, Symbol):
             raise TypeError('symbol must be a Symbol instance')
         try:
-            return self._coefficients[symbol]
+            return Rational(self._coefficients[symbol])
         except KeyError:
-            return 0
+            return Rational(0)
 
     __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):
-        return self._constant
+        return Rational(self._constant)
 
     @property
     def symbols(self):
@@ -111,8 +100,9 @@ class Expression:
         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
@@ -125,20 +115,20 @@ class Expression:
 
     @_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
-        constant = self.constant + other.constant
+        constant = self._constant + other._constant
         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
-        constant = self.constant - other.constant
+        constant = self._constant - other._constant
         return Expression(coefficients, constant)
 
     def __rsub__(self, other):
@@ -146,40 +136,19 @@ class Expression:
 
     @_polymorphic
     def __mul__(self, other):
-        if other.isconstant():
-            coefficients = dict(self.coefficients())
-            for symbol in coefficients:
-                coefficients[symbol] *= other.constant
-            constant = self.constant * other.constant
-            return Expression(coefficients, constant)
-        if isinstance(other, Expression) and not self.isconstant():
-            raise ValueError('non-linear expression: '
-                    '{} * {}'.format(self._parenstr(), other._parenstr()))
+        if isinstance(other, Rational):
+            return other.__rmul__(self)
         return NotImplemented
 
     __rmul__ = __mul__
 
     @_polymorphic
     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)
-            return Expression(coefficients, constant)
-        if isinstance(other, Expression):
-            raise ValueError('non-linear expression: '
-                '{} / {}'.format(self._parenstr(), other._parenstr()))
+        if isinstance(other, Rational):
+            return other.__rtruediv__(self)
         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
+    __rtruediv__ = __truediv__
 
     @_polymorphic
     def __eq__(self, other):
@@ -187,7 +156,7 @@ class Expression:
         # 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):
@@ -223,11 +192,13 @@ class Expression:
             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)
-                for othersymbol, coefficient in result.coefficients()
+                for othersymbol, coefficient in result._coefficients.items()
                 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
 
@@ -325,15 +296,15 @@ class 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()
+        self._coefficients = {self: 1}
+        self._constant = 0
+        self._symbols = (self,)
+        self._dimension = 1
         return self
 
     @property
@@ -343,38 +314,12 @@ class Symbol(Expression):
     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 values(self):
-        yield 1
-
     def __eq__(self, other):
         return not isinstance(other, Dummy) and isinstance(other, Symbol) \
             and self.name == other.name
@@ -406,19 +351,18 @@ class Symbol(Expression):
 
 class Dummy(Symbol):
 
-    __slots__ = (
-        '_name',
-        '_index',
-    )
-
     _count = 0
 
     def __new__(cls, name=None):
         if name is None:
             name = 'Dummy_{}'.format(Dummy._count)
         self = object().__new__(cls)
-        self._name = name.strip()
         self._index = Dummy._count
+        self._name = name.strip()
+        self._coefficients = {self: 1}
+        self._constant = 0
+        self._symbols = (self,)
+        self._dimension = 1
         Dummy._count += 1
         return self
 
@@ -441,51 +385,46 @@ def symbols(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):
-        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 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 ()
+        return Fraction.__hash__(self)
 
     @property
-    def symbols(self):
-        return ()
-
-    @property
-    def dimension(self):
-        return 0
+    def constant(self):
+        return self
 
     def isconstant(self):
         return True
 
-    def values(self):
-        yield self._constant
+    def __bool__(self):
+        return Fraction.__bool__(self)
 
     @_polymorphic
-    def __eq__(self, other):
-        return isinstance(other, Rational) and self.constant == other.constant
+    def __mul__(self, other):
+        coefficients = dict(other._coefficients)
+        for symbol in coefficients:
+            coefficients[symbol] *= self._constant
+        constant = other._constant * self._constant
+        return Expression(coefficients, constant)
 
-    def __bool__(self):
-        return self.constant != 0
+    __rmul__ = __mul__
+
+    @_polymorphic
+    def __rtruediv__(self, other):
+        coefficients = dict(other._coefficients)
+        for symbol in coefficients:
+            coefficients[symbol] /= self._constant
+        constant = other._constant / self._constant
+        return Expression(coefficients, constant)
 
     @classmethod
     def fromstring(cls, string):

diff --git a/pypol/polyhedra.py b/pypol/polyhedra.py
index 69ed2b2..e745d7d 100644 (file)
--- a/pypol/polyhedra.py
+++ b/pypol/polyhedra.py
@@ -311,16 +311,18 @@ class Polyhedron(Domain):
 def _polymorphic(func):
     @functools.wraps(func)
     def wrapper(left, right):
-        if isinstance(left, numbers.Rational):
-            left = Rational(left)
-        elif not isinstance(left, Expression):
-            raise TypeError('left must be a a rational number '
-                'or a linear expression')
-        if isinstance(right, numbers.Rational):
-            right = Rational(right)
-        elif not isinstance(right, Expression):
-            raise TypeError('right must be a a rational number '
-                'or a linear expression')
+        if not isinstance(left, Expression):
+            if isinstance(left, numbers.Rational):
+                left = Rational(left)
+            else:
+                raise TypeError('left must be a a rational number '
+                    'or a linear expression')
+        if not isinstance(right, Expression):
+            if isinstance(right, numbers.Rational):
+                right = Rational(right)
+            else:
+                raise TypeError('right must be a a rational number '
+                    'or a linear expression')
         return func(left, right)
     return wrapper
 

diff --git a/pypol/tests/test_linexprs.py b/pypol/tests/test_linexprs.py
index c55c842..6ec8993 100644 (file)
--- a/pypol/tests/test_linexprs.py
+++ b/pypol/tests/test_linexprs.py
@@ -117,11 +117,15 @@ class TestExpression(unittest.TestCase):
         self.assertEqual(self.expr * 0, 0)
         self.assertEqual(0 * self.expr, 0)
         self.assertEqual(self.expr * 2, 2*self.x - 4*self.y + 6)
+        with self.assertRaises(TypeError):
+            self.x * self.x
 
     def test_truediv(self):
         with self.assertRaises(ZeroDivisionError):
             self.expr / 0
         self.assertEqual(self.expr / 2, self.x / 2 - self.y + Fraction(3, 2))
+        with self.assertRaises(TypeError):
+            self.x / self.x
 
     def test_eq(self):
         self.assertEqual(self.expr, self.expr)
@@ -279,6 +283,10 @@ class TestRational(unittest.TestCase):
         self.assertEqual(Rational(self.pi), self.pi)
         self.assertEqual(Rational('22/7'), self.pi)
 
+    def test_hash(self):
+        self.assertEqual(hash(self.one), hash(1))
+        self.assertEqual(hash(self.pi), hash(Fraction(22, 7)))
+
     def test_isconstant(self):
         self.assertTrue(self.zero.isconstant())