[erlang-questions] Guards on assignment (i.e. assertions)

Garrett Smith <>
Mon Mar 1 21:49:22 CET 2010


On Mon, Mar 1, 2010 at 2:34 PM, Vlad Dumitrescu <> wrote:
> On Mon, Mar 1, 2010 at 21:13, Garrett Smith <> wrote:
>>> What value should A be matched to if B =< C?
>> There's no value -- the assignment fails.
>
> Ah, okay. I thought you meant something else, should have read more carefully.
>
> I think it would help reading some code, but it might be tricky to get
> the the grammar right. Could we have even
>    A = {B when B>C, D when is_list(D)}
> or only
>    A = {B, D} when B>C, is_list(D)
> ?

The guard would be applied with the assignment operator as a check
before the pattern matching was applied. So, only the second form.


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