hartthoma@linuxpt:~>cat test.hs
import Debug.Trace

foo = foldl (\first second ->
(trace ( "first: " ++ ( show first) ) first)
+
(trace ( "second: " ++ (show second) ) second) ) 0 [1,2,3]

bar = foldl (+)

traceIt x = trace ("\nTraceIt:\n"++show x++"\n") x
hartthoma@linuxpt:~>ghc -e foo test.hs
first: 0
second: 1
first: 1
second: 2
first: 3
second: 3
6
hartthoma@linuxpt:~>

hope this helps.

Ian Duncan <iand675@gmail.com>
Sent by: haskell-cafe-bounces@haskell.org

08/16/2007 08:20 PM

To	haskell-cafe@haskell.org
cc
Subject	[Haskell-cafe] Looking at program execution

Is there any way to view the steps that a haskell program goes through step by step? I'm thinking something similar to what I've seen in things I've been reading. For example: foldl (+) 0 [1..10] => (0+1) => ((0+1)+2) => (((0+1)+2)+3) => etc. I've seen these sorts of line-by-line execution steps, but I was curious if there was any way to simply type in a function and its arguments and have ghci or hugs or something print out this sort of visual representation of what's going on. Anyone know of something like this? _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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