rfc:iteration-tools

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rfc:iteration-tools [2008/11/02 23:15] – clarifications for some of the ideas presented amenthesrfc:iteration-tools [2008/11/03 14:43] – refining some ideas amenthes
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 ====Shortcomings of current tools==== ====Shortcomings of current tools====
 While these classes do their job they have some shortcomings: While these classes do their job they have some shortcomings:
-    * They only iterate over Traversables. Supporting arrays would be nice (Indeed, we have array_map(), array_walk() and some other similar functions for array processing, yet, I think we should unify these similar tools. Not to mention that array_* function do not adhere to some param order standard.+    * They only iterate over Traversables. Supporting arrays would be nice (Indeed, we have array_map(), array_walk() and some other similar functions for array processing, yet, I think we should unify these similar tools. Not to mention that array_* functions do not adhere to some param order standard.
     * FilterIterator, RecursiveFilterIterator and SearchIterator require declaration of an aditional classes that extend them     * FilterIterator, RecursiveFilterIterator and SearchIterator require declaration of an aditional classes that extend them
     * CallbackFilterIterator, although I haven't had the chance to use it, it misses one important thing. It's not passing the iterator itself as a third parameter to the callback.     * CallbackFilterIterator, although I haven't had the chance to use it, it misses one important thing. It's not passing the iterator itself as a third parameter to the callback.
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 ===map()=== ===map()===
     * Signature: array|Iterator map(array|Traversable iter, callback callback)     * Signature: array|Iterator map(array|Traversable iter, callback callback)
-    * Description: runs a function on every item in the array|Traversable and returns the results in an array|Iterator+    * Description: runs a function on every item in the array|Traversable and returns the results into an array or Iterator, depending on the first param type
     * Callback signature: mixed callback(mixed value, mixed key, array|Traversable iter)     * Callback signature: mixed callback(mixed value, mixed key, array|Traversable iter)
  
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 Although the above tools were listed as functions, as they don't do that much, they might just as well be class constructors (honestly I don't like this approach). I thought functions could do just fine because of the new namespace support that's why I represented them as such. Although the above tools were listed as functions, as they don't do that much, they might just as well be class constructors (honestly I don't like this approach). I thought functions could do just fine because of the new namespace support that's why I represented them as such.
 +Additionally, one thing I haven't represented in the above signatures is that an additional argument may be passed to the callback function representing an iteration counter.
  
 ==== Use cases ==== ==== Use cases ====
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 <?php <?php
  
-// 1.1 how could it be done right now -------------------------------------------------+// 1.1 How it could be done right now -------------------------------------------------
 class OnlyPHPFiles extends FilterIterator { class OnlyPHPFiles extends FilterIterator {
     public function accept() {     public function accept() {
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 } }
  
-// 1.2 or with the CallbackFilterIterator which I don't know with which PHP+// 1.2 Using CallbackFilterIterator which I don't know with which PHP
 // version it will be shipped // version it will be shipped
 $dirs = new CallbackFilterIterator(new DirectoryIterator(__DIR__), function($value) { $dirs = new CallbackFilterIterator(new DirectoryIterator(__DIR__), function($value) {
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-// 2.1 how could be done with my proposal --------------------------------------+// 2.1 How it could be done with my proposal --------------------------------------
 $dirs = filter(new DirectoryIterator(__DIR__), function($current, $key, $iterator) { $dirs = filter(new DirectoryIterator(__DIR__), function($current, $key, $iterator) {
     $ext = strtolower(pathinfo($this->getRealPath(), PATHINFO_EXTENSION));     $ext = strtolower(pathinfo($this->getRealPath(), PATHINFO_EXTENSION));
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 </code> </code>
  
-While the 1.2 example is very similar to 2.1 it differs from it in that it's not passing the iterator to the callback function and, of course, the fact that I use a function instead of an object. Another difference is that CallbackFilterIterator may also be used as a virtual CallbackMapIterator. For example, it's not only filtering the elements of the iterator into a new iterator, but it MAY also change those values. In my proposal, the function that changes values is map() which translates a certain value to another depending on the callback function. filter() only keeps items that validate agains certain criteria inside the callback function.+While the 1.2 example is very similar to 2.1 it differs from it in that it's not passing the iterator to the callback function and, of course, the fact that I use a function instead of an object. Another difference is that present implementation of CallbackFilterIterator (as documented on http://www.php.net/~helly/php/ext/spl/) may also be used as a virtual CallbackMapIterator. For example, it's not only filtering the elements of the iterator into a new iterator, but it MAY also change those values. In my proposal, the function that changes values is map() which translates a certain value to another depending on the callback function. filter() only keeps items that validate agains certain criteria inside the callback function. I believe a clear distinction between these features must be reflected in the API, thus two different functions in my proposal.
  
 =====Some aditional benefits===== =====Some aditional benefits=====
rfc/iteration-tools.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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