trait と generator の練習。

generator.php

<?php

trait GeneratorAction {
  private $_g;

  public function initializeGenerator($g) {
    $this->_g = $g;
  }

  public function getGenerator() {
    return $this->_g;
  }

  public function toArray() {
    $ret = array();
    foreach ($this->getGenerator() as $n) {
      $ret[] = $n;
    }
    return $ret;
  }

  public function take($take) {
    $this->_g = self::_take($this->_g, $take);
    return $this;
  }

  public function offset($offset) {
    $this->_g = self::_offset($this->_g, $offset);
    return $this;
  }

  public function select($pred) {
    $this->_g = self::_filter($this->_g, $pred);
    return $this;
  }

  public function reject($pred) {
    $reverse = static function ($n) use ($pred) { return !$pred; };
    $this->_g = self::_filter($this->_g, $reverse);
    return $this;
  }

  public function apply($func) {
    $this->_g = self::_apply($this->_g, $func);
    return $this;
  }

  private static function _take($g, $take) {
      foreach($g as $n) {
        if (--$take < 0) {
          return;
        }
        yield $n;
      }
  }

  private static function _offset($g, $offset) {
      foreach($g as $n) {
        if (0 < $offset--) {
          continue;
        }
        yield $n;
      }
  }

  private static function _filter($g, $pred) {
      foreach ($g as $n) {
        if ($pred($n)) {
          yield $n;
        }
      }
  }

  private static function _apply($g, $func) {
      foreach ($g as $n) {
          yield $func($n);
      }
  }
}

class InfinityArray {
  use GeneratorAction;

  public function __construct() {
    $this->initializeGenerator($this->infinity());
  }

  private function infinity() {
    $i = 0;
    while(++$i) {
      yield $i;
    }
  }
}

print_r(
  (new InfinityArray())
    ->offset(10)
    ->select(function($i){return $i%2==0;})
    ->take(5)
    ->toArray()
);

/*
Array
(
    [0] => 12
    [1] => 14
    [2] => 16
    [3] => 18
    [4] => 20
)
*/

print_r(
  (new InfinityArray())
    ->take(5)
    ->apply(function($n) { return $n * 2; })
    ->toArray()
);
/*
Array
(
    [0] => 2
    [1] => 4
    [2] => 6
    [3] => 8
    [4] => 10
)
*/