Implementing python slice notation

Question

I\'m trying to reimplement python slice notation in another language (php) and looking for a snippet (in any language or pseudocode) that would mimic the python logic. That is,

Answer 1

This is based on @ecatmur's Python code ported again to PHP.

= $length) {
        $endpoint = $step < 0 ? $length - 1 : $length;
    }
    return $endpoint;
}

function mySlice($L, $start = null, $stop = null, $step = null) {
    $sliced = array();
    $length = count($L);

    // adjust_slice()
    if ($step === null) {
        $step = 1;
    }
    elseif ($step == 0) {
        throw new Exception('step cannot be 0');
    }

    if ($start === null) {
        $start = $step < 0 ? $length - 1 : 0;
    }
    else {
        $start = adjust_endpoint($length, $start, $step);
    }

    if ($stop === null) {
        $stop = $step < 0 ? -1 : $length;
    }
    else {
        $stop = adjust_endpoint($length, $stop, $step);
    }

    // slice_indices()
    $i = $start;
    $result = array();
    while ($step < 0 ? ($i > $stop) : ($i < $stop)) {
        $sliced []= $L[$i];
        $i += $step;
    }
    return $sliced;
}