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Date: Fri, 26 Sep 2014 10:23:21 +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 everyone,

On 24 Sep 2014, at 23:17, Rowan Collins <rowan.collins@gmail.com> wrote:

> switch ( $number ) use ( =3D=3D=3D ) {
[...]
> switch ( $age ) use ( < ) {
[...]
> switch ( calculate_age($birth_date, $departure_date) as =
$age_at_departure ) use ( < ) {
[...]
> switch ( $product ) use ( instanceOf ) {

All of these examples are trying to reinvent concepts that can be solved =
with guards, pattern matching and overloading in other languages. In =
Erlang one can write the same function name multiple times and guard it =
("when" in fact(N)) or match the value ("0" in fact(0)).

fact(N) when N>0 ->
    N * fact(N-1);

fact(0) ->
    1.

In Scala one could replicate the instanceof behaviour by defining =
multiple methods of the same name with different argument types.

So I would rather see us making method declarations more flexible to =
cover those use cases instead of shoving all the functionality into =
switch/case. Last time I checked the interpreter to try and introduce =
more features around method declarations, it looks incredibly hard to do =
in a way that performs well. What is our stance on adding advanced =
features around declaring methods?

cu,
Lars


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