diff --git a/toy-impl/primitives.py b/toy-impl/primitives.py
index 635c5de..5b3edd6 100644
--- a/toy-impl/primitives.py
+++ b/toy-impl/primitives.py
@@ -12,6 +12,7 @@ i64 = types['int64']
 f32 = types['float']
 b = types['bool']
 I = TypeVariable('I', [i32, i64, f32])
+A = TypeVariable('A', [])
 
 def impl_math(ty):
     ty.methods['__add__'] = ([SelfType(), ty], ty, set())
@@ -66,4 +67,6 @@ i64.methods['__init__'] = ([SelfType(), I], None, {'I'})
 f32.methods['__init__'] = ([SelfType(), I], None, {'I'})
 
 simplest_ctx = Context({}, types)
+simplest_ctx.functions['len'] = ([ListType(A)], i32, {'A'})
+simplest_ctx.functions['range'] = ([i32], ListType(i32), set())