Re: [Haskell-cafe] Compiler's bane

Hi

I'm writing a simple interpretter for a small extended-lambda-calculus sort of language. And I'd just like to say... RECURSIVE LET-BINDS! GAAAAH!!! >_<

Agreed :-)

To illustrate:

let x = f x; y = 5 in x y

A simple-minded interpretter might try to replace every occurrance of "x" with "f x". This yields

let y = 5 in (f x) y

That's wrong, its a two step transformation. You just substitute all occurances of x for f x: let x = f (f x); y = 5 in (f x) y For the case let x = 5 in x, you do the same thing: let x = 5 in 5 Now as a second step you hoover up unused let bindings and disguard: 5 You seem to be combining the substitution and the removing of dead let bindings, if you separate them you should have more luck. Thanks Neil