On 06/02/2014 19:55, Tjerk Meesters wrote:
Consider the following examples for finding a value in an array:
array_search($value, $array, true);
current(array_keys($array, $value, true));
key(array_filter($array, function($item) use ($value) {
return $item === $value;
}));
Perhaps I've overlooked one way, but that's already three ways of doing
something similar; the difference lies in the memory behaviour, the first
being O(1) whereas the other two are O(n).
return array_reduce($array, function(&$result, $value, $key) use ( $fn ) {
if ( is_null($result) && $fn($value, $key) ) {
$result = $key;
}
});
}
(The invert flag would make it a little more verbose, but this would be enough for parity with array_filter() anyway.)
This would presumably have the same memory profile as a dedicated implementation (no array needs to be initialised, only the single return value), and the same worst-case time performance, but without the ability to short-cut once a match has been found.
Incidentally, in your proposal, you mentioned this:
[2] the array key is passed as the 2nd argument by using
ARRAY_USEARCH_USE_KEY
Is there a particular reason *not* to pass an extra parameter to callbacks, even if it's unused?
In the case of an existing function like array_filter(), I can see that there is a small risk of a BC break if a function was reused as the callback that could optionally take an additional parameter, and relied on that parameter not being passed in, but that seems like a bit of an edge case anyway, and doesn't apply to a brand new function.
Of couse, the proposed function can trivially be implemented with a foreach loop as well, even including a short-cut once a match has been found:
function array_usearch( $array, $fn ) {
foreach ( $array as $k => $v ) {
if ( $fn($k, $v) ) {
return $k;
}
}
return false;
}
http://codepad.viper-7.com/YM8LSs
Again, I've omitted the ability to invert the matching, but there are plenty of efficient ways of adding that.
Regards,
--
Rowan Collins
[IMSoP]