Support for dummy symbols

[linpy.git] / pypol / domains.py

diff --git a/pypol/domains.py b/pypol/domains.py
index 74351fc..224ac5f 100644 (file)
--- a/pypol/domains.py
+++ b/pypol/domains.py
@@ -5,7 +5,7 @@ import re
 from . import islhelper
 
 from .islhelper import mainctx, libisl, isl_set_basic_sets
-from .linexprs import Expression
+from .linexprs import Expression, Symbol
 
 
 __all__ = [
@@ -50,7 +50,7 @@ class Domain:
         symbols = set()
         for item in iterator:
             symbols.update(item.symbols)
-        return tuple(sorted(symbols, key=lambda symbol: symbol.name))
+        return tuple(sorted(symbols, key=Symbol.sortkey))
 
     @property
     def polyhedra(self):