Christian Stoller wrote (on 25/09/2014):
From: Rowan Collins [mailto:rowan.coll...@gmail.com], Sent: Thursday, September
25, 2014 12:31 PM
Sorry, I was talking about this bit:
Currently, switch always uses a "loose" comparison (==), so cannot
distinguish between "case 3" and "case 3.0". Occasionally, it would be
nice to switch on a strict comparison (===); but then I thought, why
stop there? What if you could use switch with any comparison operator?
My idea is to give the switch() statement an optional "use" clause
(since that's an existing keyword) containing a single comparison operator
See my earlier e-mail for examples and further details. Maybe I should
have given it its own thread so it was more visible; the idea has been
brewing for a while, I just thought this thread was a convenient place
to mention.
Ah, okay, sorry.
What do you think about that:
$value = 3;
switch (true) {
case 3.0 === $value: break;
case 3 < $value: break;
case 3 > $value: break;
}
Christian
When mixing operators like that, it makes sense to use that style -
although if you're not using fallthrough, there is little advantage over
if/elseif/else:
$value = 3;
if ( 3.0 === $value ) { }
elseif ( case 3 < $value ) { }
elseif ( case 3 > $value ) { }
At the end of the day, all control structures are glorified conditional
jumps, and most switch statements are glorified if/else blocks. To take
one of my examples from last night, you could write:
if ( $product instanceOf ProductInterfaces\Flight ) {
// ...
}
elseif ( $product instanceOf ProductInterfaces\Accomm ) {
// ...
}
else {
// ...
}
Clearly, this works, as would the same thing using switch(true) and case
instead of if/elseif, but the "$product instanceOf" has to be copied
into every clause, and someone reading the code cannot assume that all
the clauses are performing the same test.
In my proposed version, the intent is expressed more clearly, and there
is less risk of a bug being introduced by incorrect copying or refactoring:
switch ( $product ) use ( instanceOf ) {
case ProductInterfaces\Flight:
// ...
break;
case ProductInterfaces\Accomm:
// ...
break;
default:
// ...
}
That's the idea anyway.
--
Rowan Collins
[IMSoP]
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