Comment on The Haskell user experienceparentComments−sfvisser11yNote that trace is implemented in terms of unsafePerformIO (which is fine for debugging).To get a trace message, you need to attach the trace to something that does get evaluated. I mostly define a somewhat simpler helper like this: tt :: Show a => a -> a tt x = trace (show x) x So you surround your expressions with it and see there values, when those values get evaluated of course. Eg: myParser = (\_ code -> tt code) <$> parseComment <*> parseCode−jcl11yNote: I just looked at the docs linked in creichert's sibling post, and I noticed that Debug.Trace provides traceShow as a helper.
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Note that trace is implemented in terms of unsafePerformIO (which is fine for debugging).
To get a trace message, you need to attach the trace to something that does get evaluated. I mostly define a somewhat simpler helper like this:
So you surround your expressions with it and see there values, when those values get evaluated of course. Eg:Note: I just looked at the docs linked in creichert's sibling post, and I noticed that Debug.Trace provides traceShow as a helper.