[eeps] EEP XXX: Pattern-test operator

Erik Søe Sørensen <>
Fri Apr 13 13:05:55 CEST 2012


Allowing side-effects in guards would certainly not be in the Erlang
spirit.  I wouldn't dare suggesting that :-)
The left-hand expression in a pattern test expression which occurs within a
guard is naturally(?) subject to the normal constraints for what is allowed
in a guard.
I should perhaps state that explicitly in the specification.

/Erik

Den 13. apr. 2012 02.54 skrev Michael Truog <>:

> **
> Your idea is interesting.  However, doesn't it ruin the simplicity of
> guards?  It seems as if this proposal would make guards generate
> side-effects which should impact both testability and optimization
> opportunities.  Isn't this a concern?
>
>
> On 04/12/2012 04:51 PM, Erik Søe Sørensen wrote:
>
> Hello all -
>
> Attached is a proposal to add to the Erlang language an operator which
> allows for pattern matching to be used in new contexts, in particular
> within guard expressions.
>
> I hope the writeup to be in the expected format, as well as describing a
> sufficiently interesting idea.
>
> Regards,
> Erik Søe Sørensen
>
>
> _______________________________________________
> eeps mailing ://erlang.org/mailman/listinfo/eeps
>
>
>
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