Remove _repr_latex_() methods (current implementation not satisfying)

[linpy.git] / linpy / linexprs.py

diff --git a/linpy/linexprs.py b/linpy/linexprs.py
index c100698..ee6e39e 100644 (file)
--- a/linpy/linexprs.py
+++ b/linpy/linexprs.py
@@ -62,7 +62,7 @@ class LinExpr:
         symbols to their coefficients, and a constant term. The coefficients and
         the constant term must be rational numbers.
 
-        For example, the linear expression x + 2y + 1 can be constructed using
+        For example, the linear expression x + 2*y + 1 can be constructed using
         one of the following instructions:
 
         >>> x, y = symbols('x y')
@@ -76,7 +76,7 @@ class LinExpr:
 
         Alternatively, linear expressions can be constructed from a string:
 
-        >>> LinExpr('x + 2*y + 1')
+        >>> LinExpr('x + 2y + 1')
 
         A linear expression with a single symbol of coefficient 1 and no
         constant term is automatically subclassed as a Symbol instance. A linear
@@ -245,28 +245,34 @@ class LinExpr:
     @_polymorphic
     def __eq__(self, other):
         """
-        Test whether two linear expressions are equal.
+        Test whether two linear expressions are equal. Unlike methods
+        LinExpr.__lt__(), LinExpr.__le__(), LinExpr.__ge__(), LinExpr.__gt__(),
+        the result is a boolean value, not a polyhedron. To express that two
+        linear expressions are equal or not equal, use functions Eq() and Ne()
+        instead.
         """
-        if isinstance(other, LinExpr):
-            return self._coefficients == other._coefficients and \
-                self._constant == other._constant
-        return NotImplemented
-
-    def __le__(self, other):
-        from .polyhedra import Le
-        return Le(self, other)
+        return self._coefficients == other._coefficients and \
+            self._constant == other._constant
 
+    @_polymorphic
     def __lt__(self, other):
-        from .polyhedra import Lt
-        return Lt(self, other)
+        from .polyhedra import Polyhedron
+        return Polyhedron([], [other - self - 1])
+
+    @_polymorphic
+    def __le__(self, other):
+        from .polyhedra import Polyhedron
+        return Polyhedron([], [other - self])
 
+    @_polymorphic
     def __ge__(self, other):
-        from .polyhedra import Ge
-        return Ge(self, other)
+        from .polyhedra import Polyhedron
+        return Polyhedron([], [self - other])
 
+    @_polymorphic
     def __gt__(self, other):
-        from .polyhedra import Gt
-        return Gt(self, other)
+        from .polyhedra import Polyhedron
+        return Polyhedron([], [self - other - 1])
 
     def scaleint(self):
         """
@@ -339,7 +345,7 @@ class LinExpr:
         Create an expression from a string. Raise SyntaxError if the string is
         not properly formatted.
         """
-        # add implicit multiplication operators, e.g. '5x' -> '5*x'
+        # Add implicit multiplication operators, e.g. '5x' -> '5*x'.
         string = LinExpr._RE_NUM_VAR.sub(r'\1*\2', string)
         tree = ast.parse(string, 'eval')
         expr = cls._fromast(tree)
@@ -371,30 +377,6 @@ class LinExpr:
             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()):
@@ -405,7 +387,7 @@ class LinExpr:
     @classmethod
     def fromsympy(cls, expr):
         """
-        Create a linear expression from a sympy expression. Raise TypeError is
+        Create a linear expression from a SymPy expression. Raise TypeError is
         the sympy expression is not linear.
         """
         import sympy
@@ -416,7 +398,8 @@ class LinExpr:
             if symbol == sympy.S.One:
                 constant = coefficient
             elif isinstance(symbol, sympy.Dummy):
-                # we cannot properly convert dummy symbols
+                # We cannot properly convert dummy symbols with respect to
+                # symbol equalities.
                 raise TypeError('cannot convert dummy symbols')
             elif isinstance(symbol, sympy.Symbol):
                 symbol = Symbol(symbol.name)
@@ -430,7 +413,7 @@ class LinExpr:
 
     def tosympy(self):
         """
-        Convert the linear expression to a sympy expression.
+        Convert the linear expression to a SymPy expression.
         """
         import sympy
         expr = 0
@@ -477,6 +460,8 @@ class Symbol(LinExpr):
 
     @property
     def _coefficients(self):
+        # This is not implemented as an attribute, because __hash__ is not
+        # callable in __new__ in class Dummy.
         return {self: Fraction(1)}
 
     @property
@@ -516,9 +501,6 @@ class Symbol(LinExpr):
     def __repr__(self):
         return self.name
 
-    def _repr_latex_(self):
-        return '$${}$$'.format(self.name)
-
 
 def symbols(names):
     """
@@ -577,9 +559,6 @@ class Dummy(Symbol):
     def __repr__(self):
         return '_{}'.format(self.name)
 
-    def _repr_latex_(self):
-        return '$${}_{{{}}}$$'.format(self.name, self._index)
-
 
 class Rational(LinExpr, Fraction):
     """
@@ -624,13 +603,3 @@ class Rational(LinExpr, Fraction):
             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)