Improve functions Lt, Le, Eq, Ne, Ge, Gt

diff --git a/doc/reference.rst b/doc/reference.rst
index 69f0f45..e649227 100644 (file)
--- a/doc/reference.rst
+++ b/doc/reference.rst
@@ -505,7 +505,7 @@ The following functions create :class:`Polyhedron` or :class:`Domain` instances
 .. function:: Ne(expr1, expr2[, expr3, ...])
 
     Create the domain such that ``expr1 != expr2 != expr3 ...``.
-    The result is a :class:`Domain`, not a :class:`Polyhedron`.
+    The result is a :class:`Domain` object, not a :class:`Polyhedron`.
 
 .. function:: Ge(expr1, expr2[, expr3, ...])
 

diff --git a/linpy/polyhedra.py b/linpy/polyhedra.py
index b88cfd1..a720b74 100644 (file)
--- a/linpy/polyhedra.py
+++ b/linpy/polyhedra.py
@@ -364,63 +364,77 @@ class UniverseType(Polyhedron):
 Universe = UniverseType()
 
 
-def _polymorphic(func):
+def _pseudoconstructor(func):
     @functools.wraps(func)
-    def wrapper(left, right):
-        if not isinstance(left, LinExpr):
-            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, LinExpr):
-            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)
+    def wrapper(expr1, expr2, *exprs):
+        exprs = (expr1, expr2) + exprs
+        for expr in exprs:
+            if not isinstance(expr, LinExpr):
+                if isinstance(expr, numbers.Rational):
+                    expr = Rational(expr)
+                else:
+                    raise TypeError('arguments must be rational numbers '
+                        'or linear expressions')
+        return func(*exprs)
     return wrapper
 
-@_polymorphic
-def Lt(left, right):
+@_pseudoconstructor
+def Lt(*exprs):
     """
     Create the polyhedron with constraints expr1 < expr2 < expr3 ...
     """
-    return Polyhedron([], [right - left - 1])
+    inequalities = []
+    for left, right in zip(exprs, exprs[1:]):
+        inequalities.append(right - left - 1)
+    return Polyhedron([], inequalities)
 
-@_polymorphic
-def Le(left, right):
+@_pseudoconstructor
+def Le(*exprs):
     """
     Create the polyhedron with constraints expr1 <= expr2 <= expr3 ...
     """
-    return Polyhedron([], [right - left])
+    inequalities = []
+    for left, right in zip(exprs, exprs[1:]):
+        inequalities.append(right - left)
+    return Polyhedron([], inequalities)
 
-@_polymorphic
-def Eq(left, right):
+@_pseudoconstructor
+def Eq(*exprs):
     """
     Create the polyhedron with constraints expr1 == expr2 == expr3 ...
     """
-    return Polyhedron([left - right], [])
+    equalities = []
+    for left, right in zip(exprs, exprs[1:]):
+        equalities.append(left - right)
+    return Polyhedron(equalities, [])
 
-@_polymorphic
-def Ne(left, right):
+@_pseudoconstructor
+def Ne(*exprs):
     """
     Create the domain such that expr1 != expr2 != expr3 ... The result is a
-    Domain, not a Polyhedron.
+    Domain object, not a Polyhedron.
     """
-    return ~Eq(left, right)
+    domain = Universe
+    for left, right in zip(exprs, exprs[1:]):
+        domain &= ~Eq(left, right)
+    return domain
 
-@_polymorphic
-def Ge(left, right):
+@_pseudoconstructor
+def Ge(*exprs):
     """
     Create the polyhedron with constraints expr1 >= expr2 >= expr3 ...
     """
-    return Polyhedron([], [left - right])
+    inequalities = []
+    for left, right in zip(exprs, exprs[1:]):
+        inequalities.append(left - right)
+    return Polyhedron([], inequalities)
 
-@_polymorphic
-def Gt(left, right):
+@_pseudoconstructor
+def Gt(*exprs):
     """
     Create the polyhedron with constraints expr1 > expr2 > expr3 ...
     """
-    return Polyhedron([], [left - right - 1])
+    inequalities = []
+    for left, right in zip(exprs, exprs[1:]):
+        inequalities.append(left - right - 1)
+    return Polyhedron([], inequalities)