On 19/03/2015 23:55, Alex Bowers wrote:
Thats a good point, something else that just came to me; your example of $countdown[0:0]; if we had it as inclusive indexes, then this would actually give you ['Five!', 'Five!'], which is unlikely to be what was desired.
I'm not sure why it would duplicate the item like that. My interpretation of $array[$start:$end] would be "an array containing all those elements of $array with a position more than or equal to $start, but less than or equal to $end" ($position >= $start && $position <= $end).
Under that interpretation, $array[0:0] is a valid slice, of length 1, which would contain only the element of $array with position 0 (0 >= 0 && 0 <= 0).
Since you propose to preserve keys in the slice, it's actually impossible to have a duplicate item in the output anyway: if you were right and it selected the first item twice, you'd get [5 => 'Five!', 5 => 'Five!'], but keys are unique by definition, so it would end up stored as [5 => 'Five!'].
1) The range cannot be 0 in length (such that, from - to must be > 0) - This would also get around issues of people trying to use it like so : $countdown[5:3], as the expected outcome of that should be a fatal error.
$countdown[0:0] is a slice of length 1, not 0, just as $countdown[0:1] is a slice of length 2, not 1. Under my proposed definition, $countdown[5:3] could simply always return an empty array, since there is no value of $position such that ($position >= 5 && $position <= 3).
Also, your use-case of 0:0 would be better placed simply using $countdown[0].
Check my example again. $countdown[0] refers to the element with key 0, so is absolutely not a replacement for $countdown[0:0]. This is the whole point of my example.
I think the use of the @ symbol would be misplaced for this
To be clear, @ was just the first idea that came to mind, not central to my point. The point is to first create syntax for "positional access", and then extend that to "positional slice access".
A different symbol is certainly a possibility; but this is something that happens nowhere else (ignoring the & by reference) in PHP, and feels like it isn't the best solution to the problem.
I'm not sure what you mean by "something that happens nowhere else" PHP has syntax for all sorts of things, using all sorts of symbols. Your own suggestion uses the : symbol in a place where it currently can't exist.
Other languages that implement this do not require a prefixed symbol, and I don't see the need for PHP to have one.
Most languages don't need to worry about an "array" type which has keys independent from their position. PHP is the only language I know where the 0 in $foo[0] does not refer to the position in the array, but a key which can appear at any position.
2) Would a possible solution to this be just to make it explicitly clear in the documentation that this *does not* refer to the keys, and instead the array positions?
To my mind, no. Manual pages about syntax features are hard to find unless you know exactly what that syntax feature is called, and documenting an inconsistency is no substitute for avoiding that inconsistency in the first place.
Regards, -- Rowan Collins [IMSoP] -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
