Raise ValueError when sampling an empty Domain

[linpy.git] / pypol / linexprs.py

diff --git a/pypol/linexprs.py b/pypol/linexprs.py
index 9ab5c86..a9f188b 100644 (file)
--- a/pypol/linexprs.py
+++ b/pypol/linexprs.py
@@ -3,13 +3,14 @@ import functools
 import numbers
 import re
 
 import numbers
 import re
 

+from collections import OrderedDict, defaultdict

 from fractions import Fraction, gcd
 
 
 __all__ = [
     'Expression',
 from fractions import Fraction, gcd
 
 
 __all__ = [
     'Expression',

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

 ]
 
 
 ]
 
 


@@ -19,7 +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


@@ -41,47 +42,45 @@ class Expression:
         if isinstance(coefficients, str):
             if constant:
                 raise TypeError('too many arguments')
         if isinstance(coefficients, str):
             if constant:
                 raise TypeError('too many arguments')

-            return cls.fromstring(coefficients)
+            return Expression.fromstring(coefficients)
+        if coefficients is None:
+            return Rational(constant)

         if isinstance(coefficients, dict):
             coefficients = coefficients.items()
         if isinstance(coefficients, dict):
             coefficients = coefficients.items()

-        if coefficients is None:
-            return Constant(constant)
+        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 len(coefficients) == 0:
         coefficients = [(symbol, coefficient)
             for symbol, coefficient in coefficients if coefficient != 0]
         if len(coefficients) == 0:

-            return Constant(constant)
-        elif len(coefficients) == 1 and constant == 0:
+            return Rational(constant)
+        if len(coefficients) == 1 and constant == 0:

             symbol, coefficient = coefficients[0]
             if coefficient == 1:
             symbol, coefficient = coefficients[0]
             if coefficient == 1:

-                return Symbol(symbol)
+                return symbol

         self = object().__new__(cls)
         self = object().__new__(cls)

-        self._coefficients = {}
-        for symbol, coefficient in coefficients:
-            if isinstance(symbol, Symbol):
-                symbol = symbol.name
-            elif not isinstance(symbol, str):
-                raise TypeError('symbols must be strings or Symbol instances')
-            if isinstance(coefficient, Constant):
+        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 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._constant = constant

-        self._symbols = tuple(sorted(self._coefficients))
+        self._symbols = tuple(self._coefficients)

         self._dimension = len(self._symbols)
         return self
 
     def coefficient(self, symbol):
         self._dimension = len(self._symbols)
         return self
 
     def coefficient(self, symbol):

-        if isinstance(symbol, Symbol):
-            symbol = str(symbol)
-        elif not isinstance(symbol, str):
-            raise TypeError('symbol must be a string or a Symbol instance')
+        if not isinstance(symbol, Symbol):
+            raise TypeError('symbol must be a Symbol instance')

         try:
             return self._coefficients[symbol]
         except KeyError:
         try:
             return self._coefficients[symbol]
         except KeyError:


@@ -90,8 +89,7 @@ class Expression:
     __getitem__ = coefficient
 
     def coefficients(self):
     __getitem__ = coefficient
 
     def coefficients(self):

-        for symbol in self.symbols:
-            yield symbol, self.coefficient(symbol)
+        yield from self._coefficients.items()

 
     @property
     def constant(self):
 
     @property
     def constant(self):


@@ -105,6 +103,9 @@ class Expression:
     def dimension(self):
         return self._dimension
 
     def dimension(self):
         return self._dimension
 

+    def __hash__(self):
+        return hash((tuple(self._coefficients.items()), self._constant))
+

     def isconstant(self):
         return False
 
     def isconstant(self):
         return False
 


@@ -112,8 +113,7 @@ class Expression:
         return False
 
     def values(self):
         return False
 
     def values(self):

-        for symbol in self.symbols:
-            yield self.coefficient(symbol)
+        yield from self._coefficients.values()

         yield self.constant
 
     def __bool__(self):
         yield self.constant
 
     def __bool__(self):


@@ -127,12 +127,9 @@ class Expression:
 
     @_polymorphic
     def __add__(self, other):
 
     @_polymorphic
     def __add__(self, other):

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

         for symbol, coefficient in other.coefficients():
         for symbol, coefficient in other.coefficients():

-            if symbol in coefficients:
-                coefficients[symbol] += coefficient
-            else:
-                coefficients[symbol] = coefficient
+            coefficients[symbol] += coefficient

         constant = self.constant + other.constant
         return Expression(coefficients, constant)
 
         constant = self.constant + other.constant
         return Expression(coefficients, constant)
 


@@ -140,12 +137,9 @@ class Expression:
 
     @_polymorphic
     def __sub__(self, other):
 
     @_polymorphic
     def __sub__(self, other):

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

         for symbol, coefficient in other.coefficients():
         for symbol, coefficient in other.coefficients():

-            if symbol in coefficients:
-                coefficients[symbol] -= coefficient
-            else:
-                coefficients[symbol] = -coefficient
+            coefficients[symbol] -= coefficient

         constant = self.constant - other.constant
         return Expression(coefficients, constant)
 
         constant = self.constant - other.constant
         return Expression(coefficients, constant)
 


@@ -172,9 +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] = \
-                        Fraction(coefficients[symbol], other.constant)
-            constant = Fraction(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: '


@@ -184,8 +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():

-                constant = Fraction(other, self.constant)
-                return Expression(constant=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()))


@@ -196,8 +188,8 @@ class Expression:
         # "normal" equality
         # see http://docs.sympy.org/dev/tutorial/gotchas.html#equals-signs
         return isinstance(other, Expression) and \
         # "normal" equality
         # 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._coefficients == other._coefficients and \
+            self.constant == other.constant

 
     @_polymorphic
     def __le__(self, other):
 
     @_polymorphic
     def __le__(self, other):


@@ -219,14 +211,28 @@ class Expression:
         from .polyhedra import Gt
         return Gt(self, other)
 
         from .polyhedra import Gt
         return Gt(self, other)
 

-    def __hash__(self):
-        return hash((tuple(sorted(self._coefficients.items())), self._constant))
-
-    def _toint(self):
+    def scaleint(self):

         lcm = functools.reduce(lambda a, b: a*b // gcd(a, b),
             [value.denominator for value in self.values()])
         return self * lcm
 
         lcm = functools.reduce(lambda a, b: a*b // gcd(a, b),
             [value.denominator for value in self.values()])
         return self * lcm
 

+    def subs(self, symbol, expression=None):
+        if expression is None:
+            if isinstance(symbol, dict):
+                symbol = symbol.items()
+            substitutions = symbol
+        else:
+            substitutions = [(symbol, expression)]
+        result = self
+        for symbol, expression in substitutions:
+            coefficients = [(othersymbol, coefficient)
+                for othersymbol, coefficient in result.coefficients()
+                if othersymbol != symbol]
+            coefficient = result.coefficient(symbol)
+            constant = result.constant
+            result = Expression(coefficients, constant) + coefficient*expression
+        return result
+

     @classmethod
     def _fromast(cls, node):
         if isinstance(node, ast.Module) and len(node.body) == 1:
     @classmethod
     def _fromast(cls, node):
         if isinstance(node, ast.Module) and len(node.body) == 1:


@@ -236,7 +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):


@@ -257,45 +263,33 @@ class Expression:
     @classmethod
     def fromstring(cls, string):
         # add implicit multiplication operators, e.g. '5x' -> '5*x'
     @classmethod
     def fromstring(cls, string):
         # add implicit multiplication operators, e.g. '5x' -> '5*x'

-        string = cls._RE_NUM_VAR.sub(r'\1*\2', string)
+        string = Expression._RE_NUM_VAR.sub(r'\1*\2', string)

         tree = ast.parse(string, 'eval')
         return cls._fromast(tree)
 
         tree = ast.parse(string, 'eval')
         return cls._fromast(tree)
 

-    def __str__(self):
+    def __repr__(self):

         string = ''
         string = ''

-        i = 0
-        for symbol in self.symbols:
-            coefficient = self.coefficient(symbol)
+        for i, (symbol, coefficient) in enumerate(self.coefficients()):

             if coefficient == 1:
             if coefficient == 1:

-                if i == 0:
-                    string += symbol
-                else:
-                    string += ' + {}'.format(symbol)
+                string += '' if i == 0 else ' + '
+                string += '{!r}'.format(symbol)

             elif coefficient == -1:
             elif coefficient == -1:

-                if i == 0:
-                    string += '-{}'.format(symbol)
-                else:
-                    string += ' - {}'.format(symbol)
+                string += '-' if i == 0 else ' - '
+                string += '{!r}'.format(symbol)

             else:
                 if i == 0:
             else:
                 if i == 0:

-                    string += '{}*{}'.format(coefficient, symbol)
+                    string += '{}*{!r}'.format(coefficient, symbol)

                 elif coefficient > 0:
                 elif coefficient > 0:

-                    string += ' + {}*{}'.format(coefficient, symbol)
+                    string += ' + {}*{!r}'.format(coefficient, symbol)

                 else:
                 else:

-                    assert coefficient < 0
-                    coefficient *= -1
-                    string += ' - {}*{}'.format(coefficient, symbol)
-            i += 1
+                    string += ' - {}*{!r}'.format(-coefficient, symbol)

         constant = self.constant
         constant = self.constant

-        if constant != 0 and i == 0:
+        if len(string) == 0:

             string += '{}'.format(constant)
         elif constant > 0:
             string += ' + {}'.format(constant)
         elif constant < 0:
             string += '{}'.format(constant)
         elif constant > 0:
             string += ' + {}'.format(constant)
         elif constant < 0:

-            constant *= -1
-            string += ' - {}'.format(constant)
-        if string == '':
-            string = '0'
+            string += ' - {}'.format(-constant)

         return string
 
     def _parenstr(self, always=False):
         return string
 
     def _parenstr(self, always=False):


@@ -305,30 +299,27 @@ class Expression:
         else:
             return '({})'.format(string)
 
         else:
             return '({})'.format(string)
 

-    def __repr__(self):
-        return '{}({!r})'.format(self.__class__.__name__, str(self))
-

     @classmethod
     def fromsympy(cls, expr):
         import sympy
     @classmethod
     def fromsympy(cls, expr):
         import sympy

-        coefficients = {}
+        coefficients = []

         constant = 0
         for symbol, coefficient in expr.as_coefficients_dict().items():
             coefficient = Fraction(coefficient.p, coefficient.q)
             if symbol == sympy.S.One:
                 constant = coefficient
             elif isinstance(symbol, sympy.Symbol):
         constant = 0
         for symbol, coefficient in expr.as_coefficients_dict().items():
             coefficient = Fraction(coefficient.p, coefficient.q)
             if symbol == sympy.S.One:
                 constant = coefficient
             elif isinstance(symbol, sympy.Symbol):

-                symbol = symbol.name
-                coefficients[symbol] = coefficient
+                symbol = Symbol(symbol.name)
+                coefficients.append((symbol, coefficient))

             else:
                 raise ValueError('non-linear expression: {!r}'.format(expr))
             else:
                 raise ValueError('non-linear expression: {!r}'.format(expr))

-        return cls(coefficients, constant)
+        return Expression(coefficients, constant)

 
     def tosympy(self):
         import sympy
         expr = 0
         for symbol, coefficient in self.coefficients():
 
     def tosympy(self):
         import sympy
         expr = 0
         for symbol, coefficient in self.coefficients():

-            term = coefficient * sympy.Symbol(symbol)
+            term = coefficient * sympy.Symbol(symbol.name)

             expr += term
         expr += self.constant
         return expr
             expr += term
         expr += self.constant
         return expr


@@ -336,31 +327,63 @@ class Expression:
 
 class Symbol(Expression):
 
 
 class Symbol(Expression):
 

-    __slots__ = Expression.__slots__ + (
+    __slots__ = (

         '_name',
     )
 
     def __new__(cls, name):
         '_name',
     )
 
     def __new__(cls, name):

-        if isinstance(name, Symbol):
-            name = name.name
-        elif not isinstance(name, str):
-            raise TypeError('name must be a string or a Symbol instance')
-        name = name.strip()
+        if not isinstance(name, str):
+            raise TypeError('name must be a string')

         self = object().__new__(cls)
         self = object().__new__(cls)

-        self._coefficients = {name: 1}
-        self._constant = 0
-        self._symbols = tuple(name)
-        self._name = name
-        self._dimension = 1
+        self._name = name.strip()

         return self
 
     @property
     def name(self):
         return self._name
 
         return self
 
     @property
     def name(self):
         return self._name
 

+    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 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
+
+    def asdummy(self):
+        return Dummy(self.name)
+

     @classmethod
     def _fromast(cls, node):
         if isinstance(node, ast.Module) and len(node.body) == 1:
     @classmethod
     def _fromast(cls, node):
         if isinstance(node, ast.Module) and len(node.body) == 1:


@@ -372,7 +395,7 @@ class Symbol(Expression):
         raise SyntaxError('invalid syntax')
 
     def __repr__(self):
         raise SyntaxError('invalid syntax')
 
     def __repr__(self):

-        return '{}({!r})'.format(self.__class__.__name__, self._name)
+        return self.name

 
     @classmethod
     def fromsympy(cls, expr):
 
     @classmethod
     def fromsympy(cls, expr):


@@ -383,52 +406,101 @@ class Symbol(Expression):
             raise TypeError('expr must be a sympy.Symbol instance')
 
 
             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)
+        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
+
+    def __repr__(self):
+        return '_{}'.format(self.name)
+
+

 def symbols(names):
     if isinstance(names, str):
         names = names.replace(',', ' ').split()
 def symbols(names):
     if isinstance(names, str):
         names = names.replace(',', ' ').split()

-    return (Symbol(name) for name in names)
+    return tuple(Symbol(name) for name in names)
+

 
 

+class Rational(Expression):

 
 

-class Constant(Expression):
+    __slots__ = (
+        '_constant',
+    )

 
     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)

-        self._coefficients = {}
-        self._symbols = ()
-        self._dimension = 0

         return 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 ()
+
+    @property
+    def dimension(self):
+        return 0
+

     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):
         return self.constant != 0
 
     @classmethod
     def fromstring(cls, string):
     def __bool__(self):
         return self.constant != 0
 
     @classmethod
     def fromstring(cls, string):

-        if isinstance(string, str):
-            return Constant(Fraction(string))
-        else:
+        if not isinstance(string, str):

             raise TypeError('string must be a string instance')
             raise TypeError('string must be a string instance')

-
-    def __repr__(self):
-        if self.constant.denominator == 1:
-            return '{}({!r})'.format(self.__class__.__name__,
-                self.constant.numerator)
-        else:
-            return '{}({!r}, {!r})'.format(self.__class__.__name__,
-                self.constant.numerator, self.constant.denominator)
+        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 cls(expr.p, expr.q)
+            return Rational(expr.p, expr.q)

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

-            return cls(expr)
+            return Rational(expr)

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