[Haskell-cafe] An interesting paper from Google

Dan Doel dan.doel at gmail.com
Sat Oct 16 20:25:46 EDT 2010

On Saturday 16 October 2010 7:04:23 pm Ben Millwood wrote:
> On Fri, Oct 15, 2010 at 9:28 PM, Andrew Coppin
> <andrewcoppin at btinternet.com> wrote:
> > I'm still quite
> > surprised that there's no tool anywhere which will trivially print out
> > the reduction sequence for executing an expression. You'd think this
> > would be laughably easy, and yet nobody has done it yet.
> I tried to do something a bit like this:
> http://github.com/benmachine/stepeval
> but it could be charitably described as "crude": has three failing
> testcases and a bagful of unimplemented functionality.

I believe the Buddha debugger could do something like this, as well, although 
normally you wouldn't dump the entire sequence. But it has bit rotted, 
unfortunately (it's quite tied to GHC internals, as far as I can tell).

I never used it, but I've had at least one person tell me it was the best 
debugger they'd ever used. You type in an expression, and continually step 
into different parts of the reduction sequence until you find some core source 
of whatever error you're looking for.

If someone were to revive it, I'm sure many people would be appreciative.

-- Dan

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