Possible RFC - Piping operator

PipingOperator.php

/**
 * The piping operator (|>) is based on F# and LiveScript programming languages
 * or (|) on Shell and allows you to compose functions in a stack and has
 * left-associativity with lower precedence.
 */
function map(callable $fn, array $xs) {
  $acc = [];
  foreach ($xs as $x) {
    $acc[] = $fn($xs);
  }
  return $acc;
}

function filter(callable $fn, array $xs) {
  $pass = [];
  foreach ($xs as $x) {
    if ($fn($x)) {
      $pass[] = $x;
    }
  }
  return $pass;
}

function even($x) {
  return $x %% 2 === 0;
}


// With piping:

range(1, 10)
|> map (function($x) { return $x * 2 }) // => [1, 2, 3, 4 ... 20]
|> filter ('even'); // => [2,4,6,8,10,12,14,16,18,20]

// Without:

filter("even",
  map(function($x) { return $x * 2; },
    range(1, 10)));