[Haskell-cafe] Looking at program execution

[Thomas Hartman]

or actually just...

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

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

hartthoma at linuxpt:~>ghc -e foo test.hs
0+1
1+2
3+3
6
hartthoma at linuxpt:~>

is probably better




Thomas Hartman <thomas.hartman+external at db.com> 
Sent by: haskell-cafe-bounces at haskell.org
08/17/2007 10:52 AM

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haskell-cafe at haskell.org, iand675 at gmail.com
cc

Subject
Re: [Haskell-cafe] Looking at program execution







hartthoma at 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 at linuxpt:~>ghc -e foo test.hs 
first: 0 
second: 1 
first: 1 
second: 2 
first: 3 
second: 3 
6 
hartthoma at linuxpt:~> 

hope this helps. 



Ian Duncan <iand675 at gmail.com> 
Sent by: haskell-cafe-bounces at haskell.org 
08/16/2007 08:20 PM 


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haskell-cafe at haskell.org 
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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?
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