X-Git-Url: https://scm.cri.mines-paristech.fr/git/linpy.git/blobdiff_plain/ce545ffab9494e0c8250a8880859b6b097ed544d..960f0c252361dfd696359f803aae40a9b13b14a6:/pypol/linexprs.py

diff --git a/pypol/linexprs.py b/pypol/linexprs.py
index 73c6b0e..bd3ad5a 100644
--- a/pypol/linexprs.py
+++ b/pypol/linexprs.py
@@ -1,15 +1,32 @@
+# Copyright 2014 MINES ParisTech
+#
+# This file is part of Linpy.
+#
+# Linpy is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Linpy is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Linpy.  If not, see <http://www.gnu.org/licenses/>.
+
 import ast
 import functools
 import numbers
 import re
 
-from collections import OrderedDict, defaultdict
+from collections import OrderedDict, defaultdict, Mapping
 from fractions import Fraction, gcd
 
 
 __all__ = [
     'Expression',
-    'Symbol', 'symbols',
+    'Symbol', 'Dummy', 'symbols',
     'Rational',
 ]
 
@@ -31,49 +48,35 @@ 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:
             return Rational(constant)
-        if isinstance(coefficients, dict):
+        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')
-        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
+        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._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 '
-                    'or 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 number '
-                'or 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
@@ -81,19 +84,17 @@ class Expression:
     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):
-        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):
@@ -113,8 +114,9 @@ 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
@@ -127,86 +129,64 @@ 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)
 
+    @_polymorphic
     def __rsub__(self, other):
-        return -(self - other)
+        return other - self
 
-    @_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
+        if isinstance(other, numbers.Rational):
+            coefficients = ((symbol, coefficient * other)
+                for symbol, coefficient in self._coefficients.items())
+            constant = self._constant * other
             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__
 
-    @_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)
+        if isinstance(other, numbers.Rational):
+            coefficients = ((symbol, coefficient / other)
+                for symbol, coefficient in self._coefficients.items())
+            constant = self._constant / other
             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):
-        # "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 \
-            self.constant == other.constant
+            self._constant == other._constant
 
-    @_polymorphic
     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)
 
-    @_polymorphic
     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)
@@ -218,18 +198,20 @@ class Expression:
 
     def subs(self, symbol, expression=None):
         if expression is None:
-            if isinstance(symbol, dict):
+            if isinstance(symbol, Mapping):
                 symbol = symbol.items()
             substitutions = symbol
         else:
             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
 
@@ -269,41 +251,52 @@ class Expression:
 
     def __repr__(self):
         string = ''
-        i = 0
-        for symbol in self.symbols:
-            coefficient = self.coefficient(symbol)
+        for i, (symbol, coefficient) in enumerate(self.coefficients()):
             if coefficient == 1:
-                if i == 0:
-                    string += symbol.name
-                else:
-                    string += ' + {}'.format(symbol)
+                if i != 0:
+                    string += ' + '
             elif coefficient == -1:
-                if i == 0:
-                    string += '-{}'.format(symbol)
-                else:
-                    string += ' - {}'.format(symbol)
+                string += '-' if i == 0 else ' - '
+            elif i == 0:
+                string += '{}*'.format(coefficient)
+            elif coefficient > 0:
+                string += ' + {}*'.format(coefficient)
             else:
-                if i == 0:
-                    string += '{}*{}'.format(coefficient, symbol)
-                elif coefficient > 0:
-                    string += ' + {}*{}'.format(coefficient, symbol)
-                else:
-                    assert coefficient < 0
-                    coefficient *= -1
-                    string += ' - {}*{}'.format(coefficient, symbol)
-            i += 1
+                string += ' - {}*'.format(-coefficient)
+            string += '{}'.format(symbol)
         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:
-            constant *= -1
-            string += ' - {}'.format(constant)
-        if string == '':
-            string = '0'
+            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()):
@@ -339,15 +332,15 @@ 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: Fraction(1)}
+        self._constant = Fraction(0)
+        self._symbols = (self,)
+        self._dimension = 1
         return self
 
     @property
@@ -355,30 +348,7 @@ class Symbol(Expression):
         return self._name
 
     def __hash__(self):
-        return hash(self._name)
-
-    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
+        return hash(self.sortkey())
 
     def sortkey(self):
         return self.name,
@@ -386,11 +356,11 @@ class Symbol(Expression):
     def issymbol(self):
         return True
 
-    def values(self):
-        yield 1
-
     def __eq__(self, other):
-        return isinstance(other, Symbol) and self.name == other.name
+        return self.sortkey() == other.sortkey()
+
+    def asdummy(self):
+        return Dummy(self.name)
 
     @classmethod
     def _fromast(cls, node):
@@ -402,72 +372,101 @@ class Symbol(Expression):
             return Symbol(node.id)
         raise SyntaxError('invalid syntax')
 
+    def __repr__(self):
+        return self.name
+
+    def _repr_latex_(self):
+        return '$${}$$'.format(self.name)
+
     @classmethod
     def fromsympy(cls, expr):
         import sympy
-        if isinstance(expr, sympy.Symbol):
+        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):
+
+    _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._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
+
+    def __hash__(self):
+        return hash(self.sortkey())
+
+    def sortkey(self):
+        return self._name, self._index
+
+    def __repr__(self):
+        return '_{}'.format(self.name)
+
+    def _repr_latex_(self):
+        return '$${}_{{{}}}$$'.format(self.name, self._index)
+
+
 def symbols(names):
     if isinstance(names, str):
         names = names.replace(',', ' ').split()
     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._coefficients = {}
+        self._constant = Fraction(numerator, denominator)
+        self._symbols = ()
+        self._dimension = 0
+        self._numerator = self._constant.numerator
+        self._denominator = self._constant.denominator
         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
-
-    @_polymorphic
-    def __eq__(self, other):
-        return isinstance(other, Rational) and self.constant == other.constant
-
     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):