Re: [Haskell-cafe] Re: how do you debug programs?

On Thu, Sep 07, 2006 at 06:21:01AM +0100, Jn Fairbairn wrote:

David Roundy writes:

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On Wed, Sep 06, 2006 at 09:56:17AM -0700, Jason Dagit wrote:

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Or maybe even more extreme you could use template haskell or the c preprocessor to fill in the line number + column.

Which is precisely what darcs does for fromJust (which we use a lot): we define a C preprocessor macro fromJust.

Curiously, the only bug in darcs that has bitten me so far was a use of fromJust. Perhaps that indicates a weakness in the style, rather than the tools?

Yeah, in general fromJust is a dangerous business, and most of the uses of it in darcs can lead to trouble for partial repositories, for instance. I was just yesterday discussing with Jason the possibility of switching away from a Maybe approach for lazily reading patches. -- David Roundy