Do not evalf() if expression is_integer

pystencils/math_optimizations.py

@@ -18,7 +18,7 @@ try:
 
     # Evaluates all constant terms
     evaluate_constant_terms = ReplaceOptim(
-        lambda e: hasattr(e, 'is_constant') and e.is_constant,
+        lambda e: hasattr(e, 'is_constant') and e.is_constant and not e.is_integer,
         lambda p: p.evalf()
     )