[Haskell-cafe] some way to reverse engineer lambda expressionsout of the debugger?

[Thomas Hartman]

works like a charm :)

2007/1/11, Claus Reinke <claus.reinke at talk21.com>:
> > Looks very nice!
>
> thanks!-)
>
> it is far from a full-blown solution to the question in the subject, but it has its uses.
>
> > However, I'm doing my learning on ghci and got an error when I tried to load it.
> >
> > Is this hugs only, or should I try harder?
>
> I was using Hugs when I wrote that, but it works in GHC almost as well. the
> error message really ought to point to the option needed, which is -fglasgow-exts
>
> if you don't want to set the options by hand, just add the following pragma to
> the top of R.hs:
>
> {-# OPTIONS_GHC -fglasgow-exts #-}
>
> more annoying is that ghci will ignore the default directive, so you'll need to
> give explicit types when you want representations:
>
>     *Main> foldr (+) 0 [1..4]
>     10
>     *Main> foldr (+) 0 [1..4] :: R Int
>     (1 + (2 + (3 + (4 + 0))))
>     *Main> map (*) [1,2]
>
>     <interactive>:1:0:
>         No instance for (Show (t -> t))
>           arising from use of `print' at <interactive>:1:0-12
>         Possible fix: add an instance declaration for (Show (t -> t))
>         In the call (print it)
>         In the expression: print it
>         In a 'do' expression: print it
>     *Main> map (*) [1,2] :: [R Int -> R Int]
>     [\x->(1 * x),\x->(2 * x)]
>
> claus
>
> > 2007/1/11, Malcolm Wallace <Malcolm.Wallace at cs.york.ac.uk>:
> >> Bulat Ziganshin <bulat.ziganshin at gmail.com> wrote:
> >>
> >> > tphyahoo wrote:
> >> >
> >> > > *UnixTools> explodeLambda( map (*) [1,2] )
> >> > >[(\x ->> 1*x),(\x -> 2*x)]
> >>
> >> Have a play with this, from Claus Reinke:
> >>     http://www.cs.kent.ac.uk/people/staff/cr3/toolbox/haskell/R.hs
> >>
> >>
> >> Regards,
> >>     Malcolm
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