Hi
But why should c and d exist at runtime? They're only used once each, so the compiler is free to replace f with
\a b -> (a+b)+ a*b
Yes, and if the compiler is this clever, it should also be free to replace them back at debug time.
I've said this before, but I think it's worth repeating: in most cases, if you need to debug your programme it's because it's too complicated for you to understand, so the correct thing to do is to simplify it and try again.
That makes it impossible to ever improve - initially all programs are beyond you, and only by pushing the boundary do you get anywhere. As for me, I always write programs I can't understand, and that no one else can. Perhaps I understood it when I originally wrote it, perhaps not, but that was maybe over a year ago. It's been my experience that debugging is a serious weakness of Haskell - where even the poor mans printf debugging changes the semantics! And everyone comes up with arguments why there is no need to debug a functional language - that sounds more like excuses about why we can't build a good lazy debugger :) [Sorry for the slight rant, but I've used Visual Studio C++ so I know what a good debugger looks like, and how indispensable they are] Thanks Neil