[eeps] EEP XXX: Pattern-test operator
Fri Apr 27 21:12:31 CEST 2012
On Apr 23, 2012, at 19:06, "Richard O'Keefe" <> wrote:
> On 24/04/2012, at 10:52 AM, Robert Virding wrote:
>> I have missed one part of the discussion here and that is about ?=:
>> why use ?= in a guard and not =, and what does ?= mean outside a
. . .
> The problem now is that EITHER
> f(X) when X =  -> ...
> fails (because the match X =  succeeds but has value  which is
> taken as false in a guard) OR the behaviour of = in a guard is
> inconsistent with its behaviour in an expression.
> f(X = ) -> …
> f(X) when X =:=  -> …
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