rfc:generators

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rfc:generators [2012/12/23 23:44] – Add ::throw() method nikicrfc:generators [2017/09/22 13:28] (current) – external edit 127.0.0.1
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 ==== Cloning a generator ==== ==== Cloning a generator ====
  
-Generators can be cloned, thus leaving two independent ''Generator'' objects with the same state. This behavior can for example be +Generators cannot be cloned.
-used to create a ''rewindable'' function, which would make the passed generator rewindable:+
  
-<code php> +Support for cloning was included in the initial version, but removed in PHP 5.5 Beta 3 due to implementational difficulties, unclear semantics and no particularly convincing use cases.
-class RewindableGenerator implements Iterator { +
-    protected $original; +
-    protected $current; +
-     +
-    public function __construct(Generator $generator) { +
-        $this->original = $generator; +
-        $this->current = null; +
-    } +
-     +
-    public function rewind() { +
-        if ($this->current) { $this->current->close(); } +
-        $this->current = clone $this->original; +
-        $this->current->rewind(); +
-    } +
-     +
-    public function valid() { +
-        if (!$this->current) { $this->current = clone $this->original; } +
-        return $this->current->valid(); +
-    } +
-     +
-    public function current() { +
-        if (!$this->current) { $this->current = clone $this->original; } +
-        return $this->current->current(); +
-    } +
-     +
-    public function key() { +
-        if (!$this->current) { $this->current = clone $this->original; } +
-        return $this->current->key(); +
-    } +
-     +
-    public function next() { +
-        if (!$this->current) { $this->current = clone $this->original; } +
-        $this->current->next(); +
-    } +
-     +
-    public function send($value) { +
-        if (!$this->current) { $this->current = clone $this->original; } +
-        return $this->current->send($value); +
-    } +
-     +
-    public function close() { +
-        $this->original->close(); +
-        if ($this->current) { +
-            $this->current->close(); +
-        } +
-    } +
-} +
- +
-function rewindable(Generator $generator) { +
-    return new RewindableGenerator($generator); +
-} +
-</code> +
- +
-It can be then used as follows: +
- +
-<code php> +
-function xrange($start, $end, $step = 1) { +
-    for ($i = $start; $i <= $end; $i += $step) { +
-        yield $i; +
-    } +
-} +
- +
-$range = rewindable(xrange(0, 5)); +
-foreach ($range as $i) { +
-    echo $i, "\n"; +
-} +
-foreach ($range as $i) { +
-    echo $i, "\n"; +
-} +
-</code> +
- +
-This will correctly output the 0..5 range twice.+
  
 ==== Closing a generator ==== ==== Closing a generator ====
rfc/generators.1356306285.txt.gz · Last modified: 2017/09/22 13:28 (external edit)

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