Better implementation of NSAD'10 example

[linpy.git] / pypol / linexprs.py

diff --git a/pypol/linexprs.py b/pypol/linexprs.py
index ccd1564..f3cff23 100644 (file)
--- a/pypol/linexprs.py
+++ b/pypol/linexprs.py
@@ -9,8 +9,8 @@ from fractions import Fraction, gcd
 
 __all__ = [
     'Expression',
 
 __all__ = [
     'Expression',

-    'Symbol', 'symbols',
-    'Constant',
+    'Symbol', 'symbols', 'Dummy',
+    'Rational',

 ]
 
 
 ]
 
 


@@ -20,7 +20,7 @@ def _polymorphic(func):
         if isinstance(right, Expression):
             return func(left, right)
         elif isinstance(right, numbers.Rational):
         if isinstance(right, Expression):
             return func(left, right)
         elif isinstance(right, numbers.Rational):

-            right = Constant(right)
+            right = Rational(right)

             return func(left, right)
         return NotImplemented
     return wrapper
             return func(left, right)
         return NotImplemented
     return wrapper


@@ -44,7 +44,7 @@ class Expression:
                 raise TypeError('too many arguments')
             return Expression.fromstring(coefficients)
         if coefficients is None:
                 raise TypeError('too many arguments')
             return Expression.fromstring(coefficients)
         if coefficients is None:

-            return Constant(constant)
+            return Rational(constant)

         if isinstance(coefficients, dict):
             coefficients = coefficients.items()
         for symbol, coefficient in coefficients:
         if isinstance(coefficients, dict):
             coefficients = coefficients.items()
         for symbol, coefficient in coefficients:


@@ -53,7 +53,7 @@ class Expression:
         coefficients = [(symbol, coefficient)
             for symbol, coefficient in coefficients if coefficient != 0]
         if len(coefficients) == 0:
         coefficients = [(symbol, coefficient)
             for symbol, coefficient in coefficients if coefficient != 0]
         if len(coefficients) == 0:

-            return Constant(constant)
+            return Rational(constant)

         if len(coefficients) == 1 and constant == 0:
             symbol, coefficient = coefficients[0]
             if coefficient == 1:
         if len(coefficients) == 1 and constant == 0:
             symbol, coefficient = coefficients[0]
             if coefficient == 1:


@@ -61,18 +61,18 @@ class Expression:
         self = object().__new__(cls)
         self._coefficients = OrderedDict()
         for symbol, coefficient in sorted(coefficients,
         self = object().__new__(cls)
         self._coefficients = OrderedDict()
         for symbol, coefficient in sorted(coefficients,

-                key=lambda item: item[0].name):
-            if isinstance(coefficient, Constant):
+                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 numbers '
                 coefficient = coefficient.constant
             if not isinstance(coefficient, numbers.Rational):
                 raise TypeError('coefficients must be rational numbers '

-                    'or Constant instances')
+                    'or Rational instances')

             self._coefficients[symbol] = coefficient
             self._coefficients[symbol] = coefficient

-        if isinstance(constant, Constant):
+        if isinstance(constant, Rational):

             constant = constant.constant
         if not isinstance(constant, numbers.Rational):
             raise TypeError('constant must be a rational number '
             constant = constant.constant
         if not isinstance(constant, numbers.Rational):
             raise TypeError('constant must be a rational number '

-                'or a Constant instance')
+                'or a Rational instance')

         self._constant = constant
         self._symbols = tuple(self._coefficients)
         self._dimension = len(self._symbols)
         self._constant = constant
         self._symbols = tuple(self._coefficients)
         self._dimension = len(self._symbols)


@@ -127,7 +127,7 @@ class Expression:
 
     @_polymorphic
     def __add__(self, other):
 
     @_polymorphic
     def __add__(self, other):

-        coefficients = defaultdict(Constant, self.coefficients())
+        coefficients = defaultdict(Rational, self.coefficients())

         for symbol, coefficient in other.coefficients():
             coefficients[symbol] += coefficient
         constant = self.constant + other.constant
         for symbol, coefficient in other.coefficients():
             coefficients[symbol] += coefficient
         constant = self.constant + other.constant


@@ -137,7 +137,7 @@ class Expression:
 
     @_polymorphic
     def __sub__(self, other):
 
     @_polymorphic
     def __sub__(self, other):

-        coefficients = defaultdict(Constant, self.coefficients())
+        coefficients = defaultdict(Rational, self.coefficients())

         for symbol, coefficient in other.coefficients():
             coefficients[symbol] -= coefficient
         constant = self.constant - other.constant
         for symbol, coefficient in other.coefficients():
             coefficients[symbol] -= coefficient
         constant = self.constant - other.constant


@@ -166,8 +166,8 @@ class Expression:
         if other.isconstant():
             coefficients = dict(self.coefficients())
             for symbol in coefficients:
         if other.isconstant():
             coefficients = dict(self.coefficients())
             for symbol in coefficients:

-                coefficients[symbol] = Constant(coefficients[symbol], other.constant)
-            constant = Constant(self.constant, other.constant)
+                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: '
             return Expression(coefficients, constant)
         if isinstance(other, Expression):
             raise ValueError('non-linear expression: '


@@ -177,7 +177,7 @@ class Expression:
     def __rtruediv__(self, other):
         if isinstance(other, self):
             if self.isconstant():
     def __rtruediv__(self, other):
         if isinstance(other, self):
             if self.isconstant():

-                return Constant(other, self.constant)
+                return Rational(other, self.constant)

             else:
                 raise ValueError('non-linear expression: '
                         '{} / {}'.format(other._parenstr(), self._parenstr()))
             else:
                 raise ValueError('non-linear expression: '
                         '{} / {}'.format(other._parenstr(), self._parenstr()))


@@ -242,7 +242,7 @@ class Expression:
         elif isinstance(node, ast.Name):
             return Symbol(node.id)
         elif isinstance(node, ast.Num):
         elif isinstance(node, ast.Name):
             return Symbol(node.id)
         elif isinstance(node, ast.Num):

-            return Constant(node.n)
+            return Rational(node.n)

         elif isinstance(node, ast.UnaryOp) and isinstance(node.op, ast.USub):
             return -cls._fromast(node.operand)
         elif isinstance(node, ast.BinOp):
         elif isinstance(node, ast.UnaryOp) and isinstance(node.op, ast.USub):
             return -cls._fromast(node.operand)
         elif isinstance(node, ast.BinOp):


@@ -355,7 +355,7 @@ class Symbol(Expression):
         return self._name
 
     def __hash__(self):
         return self._name
 
     def __hash__(self):

-        return hash(self._name)
+        return hash(self.sortkey())

 
     def coefficient(self, symbol):
         if not isinstance(symbol, Symbol):
 
     def coefficient(self, symbol):
         if not isinstance(symbol, Symbol):


@@ -380,6 +380,9 @@ class Symbol(Expression):
     def dimension(self):
         return 1
 
     def dimension(self):
         return 1
 

+    def sortkey(self):
+        return self.name,
+

     def issymbol(self):
         return True
 
     def issymbol(self):
         return True
 


@@ -387,7 +390,11 @@ class Symbol(Expression):
         yield 1
 
     def __eq__(self, other):
         yield 1
 
     def __eq__(self, other):

-        return isinstance(other, Symbol) and self.name == other.name
+        return not isinstance(other, Dummy) and isinstance(other, Symbol) \
+            and self.name == other.name
+
+    def asdummy(self):
+        return Dummy(self.name)

 
     @classmethod
     def _fromast(cls, node):
 
     @classmethod
     def _fromast(cls, node):


@@ -414,7 +421,35 @@ def symbols(names):
     return tuple(Symbol(name) for name in names)
 
 
     return tuple(Symbol(name) for name in names)
 
 

-class Constant(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
+        Dummy._count += 1
+        return self
+
+    def __hash__(self):
+        return hash(self.sortkey())
+
+    def sortkey(self):
+        return self._name, self._index
+
+    def __eq__(self, other):
+        return isinstance(other, Dummy) and self._index == other._index
+
+
+class Rational(Expression):

 
     __slots__ = (
         '_constant',
 
     __slots__ = (
         '_constant',


@@ -422,7 +457,7 @@ class Constant(Expression):
 
     def __new__(cls, numerator=0, denominator=None):
         self = object().__new__(cls)
 
     def __new__(cls, numerator=0, denominator=None):
         self = object().__new__(cls)

-        if denominator is None and isinstance(numerator, Constant):
+        if denominator is None and isinstance(numerator, Rational):

             self._constant = numerator.constant
         else:
             self._constant = Fraction(numerator, denominator)
             self._constant = numerator.constant
         else:
             self._constant = Fraction(numerator, denominator)


@@ -455,7 +490,7 @@ class Constant(Expression):
 
     @_polymorphic
     def __eq__(self, other):
 
     @_polymorphic
     def __eq__(self, other):

-        return isinstance(other, Constant) and self.constant == other.constant
+        return isinstance(other, Rational) and self.constant == other.constant

 
     def __bool__(self):
         return self.constant != 0
 
     def __bool__(self):
         return self.constant != 0


@@ -464,14 +499,14 @@ class Constant(Expression):
     def fromstring(cls, string):
         if not isinstance(string, str):
             raise TypeError('string must be a string instance')
     def fromstring(cls, string):
         if not isinstance(string, str):
             raise TypeError('string must be a string instance')

-        return Constant(Fraction(string))
+        return Rational(Fraction(string))

 
     @classmethod
     def fromsympy(cls, expr):
         import sympy
         if isinstance(expr, sympy.Rational):
 
     @classmethod
     def fromsympy(cls, expr):
         import sympy
         if isinstance(expr, sympy.Rational):

-            return Constant(expr.p, expr.q)
+            return Rational(expr.p, expr.q)

         elif isinstance(expr, numbers.Rational):
         elif isinstance(expr, numbers.Rational):

-            return Constant(expr)
+            return Rational(expr)

         else:
             raise TypeError('expr must be a sympy.Rational instance')
         else:
             raise TypeError('expr must be a sympy.Rational instance')