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Algorithms in PHP: Deques

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Re: Algorithms in PHP: Deques

#21

Post by firasd »

jorams wrote: post #15
firasd wrote: post #14

Earlier quoted context omitted.

Actually this type of over-usage of ternary operators is not a PHP thing.. it's very prevalent in the JavaScript world

None of those snippets contain a ternary operator. ?? is the Null Coalescing Operator[1] ?-> is the nullsafe operator[2] [1]: https://www.php.net/manual/en/language.operators.comparison.... [2]: https://www.php.net/manual/en/language.oop5.basic.php#langua...

Oh my mistake. Still stuff like 'return a || b' is the kind of thing I see in JS way more than in PHP codebases

Re: Algorithms in PHP: Deques

#22

Post by actually_a_dog »

Izkata wrote: post #7
tyingq wrote: post #4

Php's array_shift() does seem unusually slow. $ time php -r '$a=array_fill(0,100000,"test");while(array_shift($a)){}' real 0m10.238s user 0m10.238s sys 0m0.000s $ time perl -e 'my @a=("test") x 100000;while(shift(@a)){}' real 0m0.027s user 0m0.027s sys 0m0.000s $ time node -e 'a=Array(100000).fill("test");while(a.shift()){}' real 0m1.350s user 0m1.343s sys 0m0.011s

PHP arrays are associative arrays, it has to update the keys for every remaining value after the first element is deleted.

That seems like some kind of local fitness minimum in the space of design choices. Even though there certainly are worse choices one could make, I couldn't imagine anything much worse than that would even stand up to any sort of use.

Re: Algorithms in PHP: Deques

#23

Post by TazeTSchnitzel »

Izkata wrote: post #7
tyingq wrote: post #4

Php's array_shift() does seem unusually slow. $ time php -r '$a=array_fill(0,100000,"test");while(array_shift($a)){}' real 0m10.238s user 0m10.238s sys 0m0.000s $ time perl -e 'my @a=("test") x 100000;while(shift(@a)){}' real 0m0.027s user 0m0.027s sys 0m0.000s $ time node -e 'a=Array(100000).fill("test");while(a.shift()){}' real 0m1.350s user 0m1.343s sys 0m0.011s

PHP arrays are associative arrays, it has to update the keys for every remaining value after the first element is deleted.

PHP does at least have an optimised internal representation for arrays with sequential integer keys, where it can avoid having a hash table and just do linear indexing: https://www.npopov.com/2014/12/22/PHPs-new-hashtable-impleme...

But a tradeoff in that design is it still has to keep track of keys and update them if you remove stuff from the start of the array. Adding and removing elements at the end is very fast, though.

Re: Algorithms in PHP: Deques

#24

Post by deergomoo »

firasd wrote: post #21
jorams wrote: post #15

Earlier quoted context omitted.

None of those snippets contain a ternary operator. ?? is the Null Coalescing Operator[1] ?-> is the nullsafe operator[2] [1]: https://www.php.net/manual/en/language.operators.comparison.... [2]: https://www.php.net/manual/en/language.oop5.basic.php#langua...

Oh my mistake. Still stuff like 'return a || b' is the kind of thing I see in JS way more than in PHP codebases

Probably because the Boolean operators in JS return the left or right side of the expression, rather than a Boolean.

It was an okay-ish way to get a default/fallback value before JS got a proper coalescing operator.

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