Hi!
On Nov 16, 2007 8:07 PM, Andras Georgy Bekes <bekesa@REDACTED> wrote:
> I'm missing a pattern match test operator from Erlang. What I mean?
> I think there should be a built-in operator, which requires a pattern on
> the left-side and a value on the right side, and returns true or false,
> depending on the success of the match.
Unless there is some use case I can't see right now, the constructs
you are suggesting are not really needed.
More precisely, I can't see when I would want to do a match against a
pattern containing only '_'s and if that is true I wouldn't need to
match again to retrieve some of the internal terms later on. In this
case, it's better to match even the internal structure from the start.
* In list comprehensions, the filtering is done automagically:
[ X || {X, _} <- L]
will simply ignore elements in L that aren't of the form {_, _}.
* One could rewrite
case Value1 of
PATTERN1 ->
case Value2 of
PATTERN2 ->
this;
_ ->
that
end;
_->
that
end
as
case {Value1, Value2} of
{PATTERN1, PATTERN2} ->
this;
_->
that
end
* Regarding
fun(Arg) when ?MATCH(PATTERN1,Arg) or ?MATCH(PATTERN2,Arg) ->
I'm not sure why you want to match Arg against two patterns. If you meant
fun(Arg1, Arg2) when ?MATCH(PATTERN1,Arg1) or ?MATCH(PATTERN2,Arg2) ->
then the usual way to do that is
fun(PATTERN1, PATTERN2) ->
So I personally don't need a match operator, it is already omnipresent
in the language.
best regards,
Vlad