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Date: Fri, 26 Sep 2014 19:41:02 +0200
Cc: internals@lists.php.net
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To: Rowan Collins <rowan.collins@gmail.com>
Subject: Re: [PHP-DEV] Little switch improvement: get the used variable
From: lars@strojny.net (Lars Strojny)

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Hi Rowan,

On 26 Sep 2014, at 18:11, Rowan Collins <rowan.collins@gmail.com> wrote:
[...]
> Without the additional guarantees provided by a purely functional =
environment, that's really just inverting the function header and if =
statement.
>=20
> Adding an extra case to that still means repeating the operator, so =
isn't the same as what I was talking about at all:
>=20
> foo(N) when N>100 ->
>    N ** foo(N-10);
>=20
> foo(N) when N>0 ->
>    N * foo(N-1);
>=20
> foo(0) ->
>    1.

That is true, for the guarding it is indeed syntactic sugar. Sugar that =
could probably help with optimisations as it makes reasoning easier from =
an interpreter perspective but still syntactic sugar.

>=20
>> In Scala one could replicate the instanceof behaviour by defining =
multiple methods of the same name with different argument types.
>=20
> Or, indeed, in most strongly typed languages; in OOP, polymorphism can =
be exploited for the same purpose, e.g. using the Visitor Pattern. =
Again, I'm not sure what this has to do with switch statements, except =
that overloading and polymorphism can both allow you to factor out *any* =
if/switch statement, if you so desire.

That is exactly my point: instead of "optimising" the switch/case =
construct which is good enough as if/elseif/else replacement I feel our =
time would be better spent on thinking of polymorphism, guards and =
pattern matching.

cu,
Lars

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