Bugfix mutator and 0 len expr

gte/__main__.py

@@ -112,6 +112,8 @@ if 'pool_size' in args:
         #        for _ in range(args.pool_size)]
     else:
         prog = rpnlib.RpnExpr.from_string(args.prog)
+        if len(prog) == 0:
+            prog = rpnlib.RpnExpr([rpnlib.RpnSymbol.from_string('0')])
         progs = [prog]
         progs += [mutate(prog, force=True) for _ in range(args.pool_size-1)]
 

gte/mutator.py

@@ -61,14 +61,14 @@ def mutadd(expr):
     return expr
 
 def mutdel(expr):
-    if len(expr) == 1:
+    if len(expr) <= 1:
         return mutadd(expr)
     pos = randint(0, len(expr)-1)
     del(expr[pos])
     return expr
 
 def mutupdtype(expr):
-    if len(expr) == 1:
+    if len(expr) <= 1:
         pos = 0
     else:
         pos = randint(0, len(expr) - 1)
@@ -78,7 +78,7 @@ def mutupdtype(expr):
     return expr
 
 def mutupdval(expr):
-    if len(expr) == 1:
+    if len(expr) <= 1:
         pos = 0
     else:
         pos = randint(0, len(expr) - 1)