[jhc] Substitutions.

Hiya, I've encountered something I don't understand in E.Subst. The substitution routine is very eager to inline stuff. It inlines all the simple applications it can find. Consider the following example: (\a -> a+a) expensive The substitution routine will inline that to: expensive+expensive Wouldn't it be prudent to generate this instead: let a = expensive in a + a Whether to inline it further would be decided later on. -- Cheers, Lemmih