Re: [Haskell-cafe] An interesting paper from Google

On Saturday 16 October 2010 7:04:23 pm Ben Millwood wrote:

On Fri, Oct 15, 2010 at 9:28 PM, Andrew Coppin

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