Re: [DISCUSS] Should RFCs for new functions include a userland polyfill/reference implementation?

Hi On 9/4/26 16:47, Larry Garfield wrote:

And that is also independent of whether it’s stdlib or a language feature (such as erased generics, which are fast, but have language design arguments against). Or in short: Performance is a property of the implementation, not a property of the feature.

I think we're saying almost the same thing, from different directions. Performance alone is not an argument for a feature, but can be a contributing factor. Performance alone MAY be an argument against a feature, depending on the feature, but there are still many other factors to consider.

The “almost” does some heavy lifting there, I believe. I disagree that performance should be a contributing factor to whether or not a proposal is good, because performance is a property of the implementation and implementation is not what is being discussed and voted on as part of the RFC process.

knowing the relative performance difference is a useful data point to have I disagree, because it rarely is an apples to apples comparison (bad userland vs good internal implementation and vice versa) and it ignores other possible solutions to fix a performance problem, for example improving the Optimizer to detect specific patterns and to transform them into equivalent, but faster code.

Using the featured RFC which proposes a function that effectively just does:

    array_filter($values, str_contains(?, 'foo'));

as an example, an alternative improvement to investigate would be replacing calls to array_filter() with PFA by a foreach loop:

    $result = [];
    foreach ($values as $key => $val) {
        if (str_contains($val, 'foo')) $result[$key] = $val;
    }

similarly to the array_map() transform that is already included in PHP 8.6. Best regards Tim Düsterhus