From 36939fa400ed913afd44b37b8bb9c1a7a932e442 Mon Sep 17 00:00:00 2001
From: Vivien Maisonneuve <v.maisonneuve@gmail.com>
Date: Thu, 19 Jun 2014 11:37:48 +0200
Subject: [PATCH] Constant names Empty and Universe, pretty printing

---
 pypol/__init__.py |  4 ++--
 pypol/linear.py   | 25 +++++++++++++++----------
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/pypol/__init__.py b/pypol/__init__.py
index a6ea752..7a195ca 100644
--- a/pypol/__init__.py
+++ b/pypol/__init__.py
@@ -4,11 +4,11 @@ A polyhedral library based on ISL.
 
 from .linear import Constant, Symbol, symbols
 from .linear import eq, le, lt, ge, gt
-from .linear import empty, universe
+from .linear import Empty, Universe
 
 
 __all__ = [
     'Constant', 'Symbol', 'symbols',
     'eq', 'le', 'lt', 'ge', 'gt',
-    'empty', 'universe'
+    'Empty', 'Universe'
 ]
diff --git a/pypol/linear.py b/pypol/linear.py
index 75ae166..3cd7633 100644
--- a/pypol/linear.py
+++ b/pypol/linear.py
@@ -11,7 +11,7 @@ __all__ = [
     'Expression', 'Constant', 'Symbol', 'symbols',
     'eq', 'le', 'lt', 'ge', 'gt',
     'Polyhedron',
-    'empty', 'universe'
+    'Empty', 'Universe'
 ]
 
 
@@ -527,7 +527,7 @@ class Polyhedron:
         other = other._toisl(symbols)
         difference = libisl.isl_set_subtract(bset, other)
         return difference
-    
+
 
     def __sub__(self, other):
         return self.difference(other)
@@ -541,10 +541,15 @@ class Polyhedron:
         return '{{{}}}'.format(', '.join(constraints))
 
     def __repr__(self):
-        equalities = list(self.equalities)
-        inequalities = list(self.inequalities)
-        return '{}(equalities={!r}, inequalities={!r})' \
-                ''.format(self.__class__.__name__, equalities, inequalities)
+        if self.isempty():
+            return 'Empty'
+        elif self.isuniverse():
+            return 'Universe'
+        else:
+            equalities = list(self.equalities)
+            inequalities = list(self.inequalities)
+            return '{}(equalities={!r}, inequalities={!r})' \
+                    ''.format(self.__class__.__name__, equalities, inequalities)
 
     def _symbolunion(self, *others):
         symbols = set(self.symbols)
@@ -572,7 +577,7 @@ class Polyhedron:
                 num = libisl.isl_val_read_from_str(_main_ctx, number)
                 iden = symbols.index(eq)
                 ceq = libisl.isl_constraint_set_coefficient_val(ceq, libisl.isl_dim_set, iden, num)  #use 3 for type isl_dim_set
-            bset = libisl.isl_basic_set_add_constraint(bset, ceq)  
+            bset = libisl.isl_basic_set_add_constraint(bset, ceq)
         for ineq in self.inequalities:
             cin = libisl.isl_inequality_alloc(libisl.isl_local_space_copy(ls))
             coeff_in = dict(ineq.coefficients())
@@ -585,7 +590,7 @@ class Polyhedron:
                 num = libisl.isl_val_read_from_str(_main_ctx, number)
                 iden = symbols.index(ineq)
                 cin = libisl.isl_constraint_set_coefficient_val(cin, libisl.isl_dim_set, iden, num)  #use 3 for type isl_dim_set
-            bset = libisl.isl_basic_set_add_constraint(bset, cin)   
+            bset = libisl.isl_basic_set_add_constraint(bset, cin)
         bset = isl.BasicSet(bset)
         return bset
 
@@ -601,8 +606,8 @@ class Polyhedron:
             our printer is giving form as:
             { [i0, i1] : 2i1 >= -2 - i0 } '''
 
-empty = None #eq(0,1)
-universe = None #Polyhedron()
+Empty = eq(0,1)
+Universe = Polyhedron()
 
 if __name__ == '__main__':
     ex1 = Expression(coefficients={'a': 6, 'b': 6}, constant= 3) #this is the expression that does not work (even without adding values)
-- 
2.20.1