[plt-dev] syntax-case error messages

By thisine of reasoning a scheme imlementation that didn't have
contracts should change car-of-null error message to say "a function
had an error" which seems wrong to me.

I agree with Jay.

Robby

On Monday, March 29, 2010, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
>
> Yeap, Lispers love that they can manipulate everything
> and complain that everything manipulates them.
>
> I think we should accept these kind of value-errors
> when we are working on our own code. When we pull in
> someone else's code and this happens, we should complain
> until he adds contracts to the module.
>
> The story for syntax looks analogous at first glance.
> But we are missing syntax-contracts. So we write down
> what we want the syntax extension to 'feel' like with
> quasi grammars and whatever. We always do this, with
> comments though. And therefore we should get errors
> at the 'upper' level.
>
> All in all, this is why I proposed the second half of
> Ryan's dissertation as a thesis-level problem, and I
> think we have mad progress.
>
>
>
>
>
> On Mar 29, 2010, at 5:30 PM, Jay McCarthy wrote:
>
>
> If I call (f 5) and the error pops up:
>
> car: expects argument of type <pair>; given 5
>
> I could say, "A mis-user of a function shouldn't need to know that the
> function is implemented with 'car' or even with pattern matching."
>
> I would say that f is a broken function because it doesn't translate
> errors in its implementation (not checking enough before calling car)
> to errors in the user's input.
>
> Similarly, I think that syntax-case errors should say 'syntax-case' in
> them. If a macro lets such an error escape, then it is a bad macro,
> just like f would be a bad function.
>
> In practice this means that good syntax-case macros have a clause:
>
> [_ (raise-syntax-error 'macro "My syntax is ...." stx)]
>
> Jay
>
> On Mon, Mar 29, 2010 at 2:43 PM, Matthias Felleisen
> <matthias at ccs.neu.edu> wrote:
>
>
> On Mar 29, 2010, at 4:39 PM, Matthew Flatt wrote:
>
>
> For now, I'm opposed to either change. A mis-user of a syntactic form
> shouldn't need to know that the form is implemented with `syntax-case'
> or even with pattern matching.
>
>
>
> Eugene Kohlbecker would whole-heartedly agree here. Let's not confuse how a
> macro is implemented with what it supposed to
> do._________________________________________________
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>
>
>
>
> --
> Jay McCarthy <jay at cs.byu.edu>
> Assistant Professor / Brigham Young University
> http://teammccarthy.org/jay
>
> "The glory of God is Intelligence" - D&C 93
>
>
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