Re: [Haskell-cafe] Printing call site for partial functions

Michael Snoyman writes:

I had a bug in a site of mine[1] for a few weeks, where it would just print:

Prelude.head: empty list

It took a long time to track down the problem

+1: I've been arguing this for something like ten years :-) One half-baked quasi-solution is to use: #define head (\xs -> case xs of { (x:_) -> x ; _ -> error("head: empty list at"++__FILE__++show __LINE__)}) Downsides are that it depends on CPP, and, CPP being a C preprocessor, it doesn't blend well with lines with single apostrophes on them (e.g.: head x') -k -- If I haven't seen further, it is by standing in the footprints of giants