Common debugging/error/exception functions that give file location information
$(err "OH NO!") main:Main main.hs:16:1 OH NO!
Notice how it displays package:module file:line:character
It exposes the functions err (error), undef (undefined), and trc (Debug.Trace.trace). All of these behave the same as their normal counterpart but also spit out a location.
Here is my favorite helper, debug, which is like trace but just show the value.
debug [1,2,3] DEBUG: [1,2,3] [1,2,3]
And The Template Haskell version.
$(dbg) [1,2,3] DEBUG main:Main main.hs:1:3 [1,2,3] [1,2,3]
Also there is a version of thrwIO that gives location information
($(thrwIO) $ AException)
catche -> putStrLn ("Caught " ++ show (e :: AException)) Caught AException "main:Main test/main.hs:25:6"
See module for a listing of all the functions with short descriptions, and the homepage for some more examples https://github.com/gregwebs/ErrorLocation.hs