How to [temporarily] suppress “defined but not used” warnings?

Question

When I prototype Haskell programs, I always get hundreds of warnings like this (not joking):

/Users/bob/SourceCode/course/is/expriment/LiftedSpine2.hs:70:15:
    W         


        

Answer 1

I usually use -w to suppress all warnings when I want get rid of some warning temporarily.

Answer 2

Another possibility, depending on your situation: I believe you can prefix identifiers with an underscore to suppress this warning. So:

_x = 42

will not generate the warning if _x is not used.

Answer 3

GHC has two warnings flags which can trigger Warning: Defined but not used.

You need some combination of the command line flags -fno-warn-unused-binds and -fno-warn-unused-matches.

Answer 4

I use a workaround for this:

I compile without warnings, but then I use HLint tool to display warnings for me. HLint has facilities to turn warnings separately.