Online PHP editor | output for s7JJO

@ 2015-04-29T20:37:54Z

<?php

function entropy($a, $b) {
  $options = array_filter(func_get_args());
  $total = array_sum($options);

  $entropy = 0;
  foreach ($options as $size) {
    $part = $size / $total;
    $entropy -= $part * log($part, 2);
  }

  return $entropy;
}

var_dump('1 4', entropy(1, 4)); // abbbb
echo "\n";

var_dump('2 2', entropy(2, 2)); // aabb
echo "\n";

var_dump('2 2 2', entropy(2, 2, 2)); // aabbcc
echo "\n";

var_dump('2 2 2 2', entropy(2, 2, 2, 2)); // aabbccdd
echo "\n";

Output for 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6: string(3) "1 4" float(0.7219280948873623) string(3) "2 2" float(1) string(5) "2 2 2" float(1.584962500721156) string(7) "2 2 2 2" float(2)
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.8 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33: string(3) "1 4" float(0.72192809488736) string(3) "2 2" float(1) string(5) "2 2 2" float(1.5849625007212) string(7) "2 2 2 2" float(2)

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