Added some docs

[linpy.git] / pypol / polyhedra.py

diff --git a/pypol/polyhedra.py b/pypol/polyhedra.py
index f8d413e..fe143d4 100644 (file)
--- a/pypol/polyhedra.py
+++ b/pypol/polyhedra.py
@@ -56,14 +56,23 @@ class Polyhedron(Domain):
 
     @property
     def equalities(self):
+    """
+    Return a list of the equalities in a set.
+    """
         return self._equalities
 
     @property
     def inequalities(self):
+    """
+    Return a list of the inequalities in a set.
+    """
         return self._inequalities
 
     @property
     def constraints(self):
+    """
+    Return ta list of the constraints of a set.
+    """
         return self._constraints
 
     @property
@@ -72,13 +81,13 @@ class Polyhedron(Domain):
 
     def disjoint(self):
         """
-        Return this set as disjoint.
+        Return a set as disjoint.
         """
         return self
 
     def isuniverse(self):
         """
-        Return true if this set is the Universe set.
+        Return true if a set is the Universe set.
         """
         islbset = self._toislbasicset(self.equalities, self.inequalities,
             self.symbols)
@@ -88,7 +97,7 @@ class Polyhedron(Domain):
 
     def aspolyhedron(self):
         """
-        Return polyhedral hull of this set.
+        Return polyhedral hull of a set.
         """
         return self
 
@@ -106,18 +115,42 @@ class Polyhedron(Domain):
         return True
 
     def subs(self, symbol, expression=None):
+    """
+    Subsitute the given value into an expression and return the resulting expression.
+    """
         equalities = [equality.subs(symbol, expression)
             for equality in self.equalities]
         inequalities = [inequality.subs(symbol, expression)
             for inequality in self.inequalities]
         return Polyhedron(equalities, inequalities)
 
+    def _asinequalities(self):
+        inequalities = list(self.equalities)
+        inequalities.extend([-expression for expression in self.equalities])
+        inequalities.extend(self.inequalities)
+        return inequalities
+
+    def widen(self, other):
+        if not isinstance(other, Polyhedron):
+            raise ValueError('argument must be a Polyhedron instance')
+        inequalities1 = self._asinequalities()
+        inequalities2 = other._asinequalities()
+        inequalities = []
+        for inequality1 in inequalities1:
+            if other <= Polyhedron(inequalities=[inequality1]):
+                inequalities.append(inequality1)
+        for inequality2 in inequalities2:
+            for i in range(len(inequalities1)):
+                inequalities3 = inequalities1[:i] + inequalities[i + 1:]
+                inequalities3.append(inequality2)
+                polyhedron3 = Polyhedron(inequalities=inequalities3)
+                if self == polyhedron3:
+                    inequalities.append(inequality2)
+                    break
+        return Polyhedron(inequalities=inequalities)
+
     @classmethod
     def _fromislbasicset(cls, islbset, symbols):
-        if libisl.isl_basic_set_is_empty(islbset):
-            return Empty
-        if libisl.isl_basic_set_is_universe(islbset):
-            return Universe
         islconstraints = islhelper.isl_basic_set_constraints(islbset)
         equalities = []
         inequalities = []
@@ -198,6 +231,7 @@ class Polyhedron(Domain):
         else:
             return 'And({})'.format(', '.join(strings))
 
+
     def _repr_latex_(self):
         strings = []
         for equality in self.equalities:
@@ -208,12 +242,18 @@ class Polyhedron(Domain):
 
     @classmethod
     def fromsympy(cls, expr):
+    """
+    Convert a sympy object to an expression.
+    """
         domain = Domain.fromsympy(expr)
         if not isinstance(domain, Polyhedron):
             raise ValueError('non-polyhedral expression: {!r}'.format(expr))
         return domain
 
     def tosympy(self):
+    """
+    Return an expression as a sympy object. 
+    """
         import sympy
         constraints = []
         for equality in self.equalities:
@@ -222,7 +262,6 @@ class Polyhedron(Domain):
             constraints.append(sympy.Ge(inequality.tosympy(), 0))
         return sympy.And(*constraints)
 
-
 class EmptyType(Polyhedron):
 
     __slots__ = Polyhedron.__slots__
@@ -236,6 +275,11 @@ class EmptyType(Polyhedron):
         self._dimension = 0
         return self
 
+    def widen(self, other):
+        if not isinstance(other, Polyhedron):
+            raise ValueError('argument must be a Polyhedron instance')
+        return other
+
     def __repr__(self):
         return 'Empty'
 
@@ -288,41 +332,42 @@ def _polymorphic(func):
 @_polymorphic
 def Lt(left, right):
     """
-    Return true if the first set is less than the second.
+    Assert first set is less than the second set.
     """
     return Polyhedron([], [right - left - 1])
 
 @_polymorphic
 def Le(left, right):
     """
-    Return true the first set is less than or equal to the second.
+    Assert first set is less than or equal to the second set.
     """
     return Polyhedron([], [right - left])
 
 @_polymorphic
 def Eq(left, right):
     """
-    Return true if the sets are equal.
+    Assert first set is equal to the second set.
     """
     return Polyhedron([left - right], [])
 
 @_polymorphic
 def Ne(left, right):
     """
-    Return true if the sets are NOT equal.
+    Assert first set is not equal to the second set.
     """
     return ~Eq(left, right)
 
 @_polymorphic
 def Gt(left, right):
     """
-    Return true if the first set is greater than the second set.
+    Assert first set is greater than the second set.
     """
     return Polyhedron([], [left - right - 1])
 
 @_polymorphic
 def Ge(left, right):
     """
-    Return true if the first set is greater than or equal the second set.
+    Assert first set is greater than or equal to the second set.
     """
     return Polyhedron([], [left - right])
+