Dennis Raddle
Haskell creates compile-time error messages that are somewhat hard to understand for beginners.
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One reason for the weird (to a beginner) compile errors in Haskell is its expressivity -- almost any sequence of identifiers could potentially mean something, and if you make a mistake, the compiler is sure to find some "weird" way to interpret it.
I think the main source of weird error messages is Haskell's support for type classes. Remember all those compiler's complaints about missing instances? Those are probably the most confusing ones for beginners: main = print (sin + 3) You just forgot the argument to sin, for which an appropriate error message would be something like "missing argument" or "first argument of (+) is not a number". Of course the former is impossible in Haskell because of currying. The latter would be possible, if Haskell wouldn't have type classes (you would get a regular type mismatch). Instead you get two missing instance errors: No instance for (Show (a0 -> a0)) arising from a use of `print' No instance for (Num (a0 -> a0)) arising from a use of `+' I think that this problem cannot be solved, but one possible improvement is for the compiler to print suggestions taken from a database. Something along the lines of: Notice: You probably forgot to apply `sin' to an argument. However, I think that no work is done on that, and there is another possible path: An average Haskell tutorial should always include a section on understanding error messages. In fact the latest issue of The Monad Reader [1] has an article on that by Jan Stolarek. [1]: http://themonadreader.files.wordpress.com/2012/08/issue20.pdf Greets, Ertugrul -- Not to be or to be and (not to be or to be and (not to be or to be and (not to be or to be and ... that is the list monad.