On Wed, Jun 26, 2013 at 11:20 PM, Jeremy Curcio <j.cur...@icloud.com> wrote:
> Hello,
>
> I would like to submit an RFC to add a new function to the PHP language.
> The function would be called "map()". The purpose of this function would be
> to take an existing value within a range and make it to a corresponding
> location within a new range.
>
> The map() method would have 5 required parameters, $originalLow,
> $originalHigh, $newLow, $newHigh, and $value.
>
> map() would be implement the following:
>
> function map($originalLow, $originalHigh, $newLow, $newHigh, $value) {
> return $newLow + ($value - $originalLow) * ($newHigh - $newLow) /
> ($originalHigh- $originalLow);
> }
>
>
Purely from a development perspective, having five required function
arguments is bad; it can be reduced (by treating the first four as two
ranges) to three arguments, e.g.
map([55, 92], [70, 100], 55);
You can go one step further and call it what it is, not a mapper, but a
single dimensional range transformer and use a closure, e.g.:
$transformer = get_1d_range_transformer([55, 92], [70, 100]);
echo $transformer(55); // get transformed value
You might also benefit from an OOP approach. I won't paste it here, but
I've created a pastie for it: http://codepad.org/nGZv8GJa
It's debatable whether this somewhat specialized code would need to be
coded at something other than the language level; in most likelihood you
won't gain any appreciable performance increase.
> Example:
> Let's say we are teachers and are grading final exams. We have a policy
> that the best score is 100, and the worst score is a 70. Students scored
> between 55 and 92. We want to easily re-score the exams to be within the
> new score range, so we would use the new map() function. Let's begin with
> mapping the lowest score:
>
> $newScore = map(55, 92, 70, 100, 55); //$newScore = 70
>
> If we have all of our scores in an array:
>
> $scores = array(71, 65, 55, 85, 88, 86, 92, 77, 73);
>
> We could use a foreach loop to remap each value:
>
> $newScores = array();
> foreach($score as $scores) {
> $newScores[] = map(55, 92, 70, 100, $score);
> }
> var_dump($newScores);
> /*
> array(9) {
> [0]=>
> float(82.972972972973)
> [1]=>
> float(78.108108108108)
> [2]=>
> int(70)
> [3]=>
> float(94.324324324324)
> [4]=>
> float(96.756756756757)
> [5]=>
> float(95.135135135135)
> [6]=>
> int(100)
> [7]=>
> float(87.837837837838)
> [8]=>
> float(84.594594594595)
> }
> */
>
> Just like that, we have the new exam grades that fit our policy, within
> the proper scale, without having to do any of the messy math ourselves.
>
> While I do recognize that this is somewhat trivial to anyone who knows the
> proper formula, I feel as though it would serve the PHP community well.
> Much the same as the pow() or pi() functions do. I appreciate your thoughts
> on this matter and whether or not this is worth pursuing as an RFC.
>
> Thank you,
> Jeremy Curcio
> j.cur...@me.com
>
--
--
Tjerk
