[Haskell-cafe] debugtracehelpers Re: traceM and traceShowM
Alberto G. Corona
agocorona at gmail.com
Tue Oct 20 15:14:13 EDT 2009
I don't know why people use trace this way instead of in the reverse form:
debug = flip trace
this way I can isolate debug code in the right from normal code:
a <- getChar
b <- getChar `debug` ("a="++ show a)
let c= a+b `debug` ("b="++ show b)
and so on.
I saw it for the first time in the DrIFt libtary.
2009/10/20 Justin Bailey <jgbailey at gmail.com>
> These woudl be much more useful if they flushed the output handle
> after each message. Then you know your trace messages will be
> displayed/written to a file.
> On Mon, Oct 19, 2009 at 1:51 PM, Thomas Hartman <tphyahoo at gmail.com>
> > I have this and a couple other handy functions in
> > DebugTraceHelpers:
> > hackage:
> > 2009/10/16 Martijn van Steenbergen <martijn at van.steenbergen.nl>:
> >> Hello,
> >> I propose the addition of the following two functions to module
> >>> traceM :: Monad m => String -> m ()
> >>> traceM msg = trace msg (return ())
> >>> traceShowM :: (Show a, Monad m) => a -> m ()
> >>> traceShowM = traceM . show
> >> These functions allow tracing in any do-block. I often define them
> myself; I
> >> think they are useful in general.
> >> Deadline: 23 October 2009.
> >> Martijn.
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