From:
Operating system: Irrelevant
PHP version: 5.3.2
Package: *Programming Data Structures
Bug Type: Feature/Change Request
Bug description:yield syntax construct
Description:
------------
I draw your attention to the "yield" construct as used in Python, (recent)
JavaScript, and C#. This would be I think a nice way of creating Iterators
for traversing complex objects.
A method that uses "yield" can be replaced by one that declares an instance
of a custom implementation of Iterator that takes $this and the method's
arguments in its constructor, and cranks through a state machine on each
call of next(). (Microsoft's C# compiler handles it in essentially this
way, but has a much harder time of it because of things like multithreading
and explicit resource disposal.)
To some extent this can be done by hand now (I've done some work on a
preprocessing script that automates this) but in the absence of inner
classes (which is what this Iterator ought to be) - hint, hint - it plays
havoc with visibility attributes.
Expected result:
----------------
/*
Example method that produces an inorder traversal of a binary tree.
foreach($btree->traverse_inorder() as $node)
{
do_something_with($node);
}
*/
public function traverse_inorder()
{
foreach($this->left->traverse_inorder() as $child)
{
yield $child;
}
yield $this;
foreach($this->right->traverse_inorder() as $child)
{
yield $child;
}
}
Actual result:
--------------
/*
The state machine that implements the body of the test script's function
(identifies if the end of the traversal has been reached, and obtains the
next value to return if not)
*/
do
{
switch($this->_state)
{
case -1:
return false;
case 0:
// the object being traversed needs "left" made public
$this->_t1 = $this->_this->left->traverse_inorder();
reset($this->_t1);
$this->_state = 1;
case 1:
if(!($e = each($this->_t1)))
{
$this->_t1 = null;
$this->_state = 2;
continue;
}
$this->_value = $e['value'];
return true;
case 2:
$this->_value = $this->_this;
$this->_state = 3;
return true;
case 3:
// the object being traversed needs "right" made public
$this->_t2 = $this->_this->right->traverse_inorder();
reset($this->_t2);
$this->_state = 4;
case 4:
if(!($e = each($this->_t2)))
{
$this->_t2 = null;
$this->_state = -1;
return false;
}
$this->_value = $e['value'];
return true;
}
} while(false);
--
Edit bug report at http://bugs.php.net/bug.php?id=51460&edit=1
--
Try a snapshot (PHP 5.2):
http://bugs.php.net/fix.php?id=51460&r=trysnapshot52
Try a snapshot (PHP 5.3):
http://bugs.php.net/fix.php?id=51460&r=trysnapshot53
Try a snapshot (PHP 6.0):
http://bugs.php.net/fix.php?id=51460&r=trysnapshot60
Fixed in SVN:
http://bugs.php.net/fix.php?id=51460&r=fixed
Fixed in SVN and need be documented:
http://bugs.php.net/fix.php?id=51460&r=needdocs
Fixed in release:
http://bugs.php.net/fix.php?id=51460&r=alreadyfixed
Need backtrace:
http://bugs.php.net/fix.php?id=51460&r=needtrace
Need Reproduce Script:
http://bugs.php.net/fix.php?id=51460&r=needscript
Try newer version:
http://bugs.php.net/fix.php?id=51460&r=oldversion
Not developer issue:
http://bugs.php.net/fix.php?id=51460&r=support
Expected behavior:
http://bugs.php.net/fix.php?id=51460&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=51460&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=51460&r=submittedtwice
register_globals:
http://bugs.php.net/fix.php?id=51460&r=globals
PHP 4 support discontinued: http://bugs.php.net/fix.php?id=51460&r=php4
Daylight Savings: http://bugs.php.net/fix.php?id=51460&r=dst
IIS Stability:
http://bugs.php.net/fix.php?id=51460&r=isapi
Install GNU Sed:
http://bugs.php.net/fix.php?id=51460&r=gnused
Floating point limitations:
http://bugs.php.net/fix.php?id=51460&r=float
No Zend Extensions:
http://bugs.php.net/fix.php?id=51460&r=nozend
MySQL Configuration Error:
http://bugs.php.net/fix.php?id=51460&r=mysqlcfg
