[mercury-users] errors with typeclasses

[Ralph Becket]

>From Fergus Henderson on 02/11/2000 16:57:59
> For type class method implementations, we treat e.g.
> 
> 	:- instance foo(bar) where [
> 		pred(baz/3) is quux
> 	].
> 
> as just an abbreviation for
> 
> 	:- instance foo(bar) where [
> 		baz(A,B,C) :- quux(A,B,C)
> 	].
> 
> So there's no explicit call, but there's an implicit call.

That's true.
> 
> It would not be hard to change the error message to "in argument N of
> implicit call to predicate ..." or to just "in argument of predicate ...".

"in argument N of predicate..." would be better, I think.  "in argument N
of method implementation..." would be great, but possibly a bit too wordy?

--
Ralph Becket      |      MSR Cambridge      |      rbeck at microsoft.com 

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