Function to output function name

Question

Is it possible in Haskell to implement a function which returns its own function name?

A possible type could be (a -> b) -> String.

Answer 1

You can preprocess your source code with CPP. In CPP

#define _NAMEOF(name) #name

defines a macro, _NAMEOF, for stringifying text (including surrounding it with programmer's quotation marks). You can then use it as follows:

head [] = error $ _NAMEOF(head) ++ ": empty list!"

which CPP should translate into a valid Haskell source code line:

head [] = error $ "head" ++ ": empty list!"