rfc:pow-operator

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rfc:pow-operator [2013/12/19 01:56] – datibbawrfc:pow-operator [2014/02/07 06:46] – Better (consistent) wording bwoebi
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 ====== PHP RFC: Power Operator ====== ====== PHP RFC: Power Operator ======
-  * Version: 0.1+  * Version: 0.3
   * Date: 2013-11-23   * Date: 2013-11-23
   * Author: Tjerk Meesters, datibbaw@php.net   * Author: Tjerk Meesters, datibbaw@php.net
-  * Status: Voting+  * Status: Implemented in PHP 5.6
   * First Published at: http://wiki.php.net/rfc/pow-operator   * First Published at: http://wiki.php.net/rfc/pow-operator
 +  * Revision (0.1 → 0.2): 2013-12-19
 +  * Revision (0.2 → 0.3): 2013-12-21
  
 ===== Introduction ===== ===== Introduction =====
  
-This proposal is three-fold:+This proposal is two-fold:
  
-  - Turn the existing [[http://php.net/pow|pow()]] function into a language construct.+  - Introduce an exponential (right associative) operator ''<nowiki>**</nowiki>''.
     * Avoids a function call.     * Avoids a function call.
     * Support for [[rfc:operator_overloading_gmp|GMP overloading]].     * Support for [[rfc:operator_overloading_gmp|GMP overloading]].
-  - Introduce an exponential (right associative) operator ''<nowiki>**</nowiki>''. 
     * Easier to read and shorter to write.     * Easier to read and shorter to write.
     * Can be found in other languages.     * Can be found in other languages.
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 ===== Proposal ===== ===== Proposal =====
- 
-**pow() as language construct** 
- 
-No changes to existing code, safe for one: 
- 
-<code php> 
-var_dump(pow([], 2)); // int(0) instead of float(0) 
-</code> 
- 
-**Power operator** 
  
 A short working example: A short working example:
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 The operator precedence is: The operator precedence is:
-  * higher than the bitwise not (~), +  * higher than the bitwise not (~) and unary minus, 
-  * lower than array dereferencing, +  * lower than array dereferencing.
-  * lower than unary minus.+
  
 Examples: Examples:
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 <code php> <code php>
 echo 2 ** 3 ** 2; // 512 (not 64) echo 2 ** 3 ** 2; // 512 (not 64)
-echo -3 ** 2; // 9 (not -9)+echo -3 ** 2; // -9 (not 9) 
 +echo 1 - 3 ** 2; // -8
 echo ~3 ** 2; // -10 (not 16) echo ~3 ** 2; // -10 (not 16)
 </code> </code>
 +
 +===== Changelog =====
 +
 +21-Dec-2013: 
 +  * Removed turning pow() into a language construct from the proposal, due to BC breaks.
 +  * Closed vote and moved RFC back to Discussion status.
 +  * Reverted commit [[https://github.com/datibbaw/php-src/commit/f60b98cf7a8371233d800a6faa286ddba4432d02|f60b98c]].
 +
 +22-Dec-2013:
 +  * Moved RFC back to Voting status
  
 ===== Discussion ===== ===== Discussion =====
 +
 +> Should ''-2 <nowiki>**</nowiki> 3'' evaluate to ''9'' instead of ''-9''?
 +
 +According to the following resources, the scale tips more towards having the exponent precede the unary minus:
 +
 +  * http://mathforum.org/library/drmath/view/53194.html
 +  * http://math.stackexchange.com/questions/491933/exponent-rules-with-negative-numbers
 +  * http://math.stackexchange.com/questions/68833/what-does-22-evaluate-to/68834#68834
 +
 +**Similar languages**
 +
 +  * Ada
 +  * D
 +  * F#
 +  * Fortran
 +  * Freemat
 +  * Haskell
 +  * Mathematica / Matlab / Scilab
 +  * Octave
 +  * Perl
 +  * Python
 +  * R
 +  * Ruby
 +  * Sage
 +  * VB / Basic
 +
 +**Dissimilar languages**
 +
 +  * Bash
 +  * Cobol
 +  * ColdFusion
 +  * Excel
 +  * Tcl
 +
 +----
  
 > Should ''2 <nowiki>**</nowiki> 3 <nowiki>**</nowiki> 2'' yield ''64'' (left associative), ''512'' (right associative) or throw an error (non associative)? > Should ''2 <nowiki>**</nowiki> 3 <nowiki>**</nowiki> 2'' yield ''64'' (left associative), ''512'' (right associative) or throw an error (non associative)?
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   * Octave   * Octave
   * Matlab   * Matlab
-  * D 
   * ColdFusion   * ColdFusion
  
 ** Languages with right associative exponential operator** ** Languages with right associative exponential operator**
  
 +  * D
   * Haskell   * Haskell
   * R   * R
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 External extensions such as [[http://pecl.php.net/package/vld|vld]] or [[https://github.com/krakjoe/phpdbg|phpdbg]] would have to be updated, but I'm not aware of any core extensions that would otherwise be affected. External extensions such as [[http://pecl.php.net/package/vld|vld]] or [[https://github.com/krakjoe/phpdbg|phpdbg]] would have to be updated, but I'm not aware of any core extensions that would otherwise be affected.
  
-===== Open Issues ===== +===== Vote =====
- +
-None. +
- +
- +
-===== Proposed Voting Choices =====+
  
 Voting will be based on the following: Voting will be based on the following:
  
-  * Turn ''pow()'' into a language construct, 
   * Add the power operators ''<nowiki>**</nowiki>'' and ''<nowiki>**</nowiki>='',   * Add the power operators ''<nowiki>**</nowiki>'' and ''<nowiki>**</nowiki>='',
   * Add ''ZEND_POW'' and ''ZEND_ASSIGN_POW'' opcodes.   * Add ''ZEND_POW'' and ''ZEND_ASSIGN_POW'' opcodes.
 +
 +Changes from 0.1:
 +
 +  * A option is added to vote for a non-associative ''<nowiki>**</nowiki>'' operator. See also: Discussion. This counts as an inclusion vote.
 +
 +A two third majority is required for acceptance.
  
 ---- ----
  
-<doodle title="Should PHP get a power operator in PHP 5.6?" auth="datibbaw" voteType="single" closed="false"> +<doodle title="Should PHP get a power operator in 5.6?" auth="datibbaw" voteType="single" closed="true"> 
-   * Yes+   * Yes, right associative 
 +   * Yes, non associative
    * No    * No
 </doodle> </doodle>
- 
-Voting ends on 31st of December. 
  
 ---- ----
 +
 +Voting ends on 5th of January 2014.
 +
 +
 +
 ===== Patches and Tests ===== ===== Patches and Tests =====
  
 Power operator PR: https://github.com/php/php-src/pull/543 Power operator PR: https://github.com/php/php-src/pull/543
  
 +PHP 5.6 Commits: [[http://git.php.net/?p=php-src.git;a=commit;h=aff56f3c4539869910cf2778cf0ece2d8c2dd671|1]] [[http://git.php.net/?p=php-src.git;a=commit;h=363ff60475d93716722034b8f7a2486229bf4cfb|2]]
rfc/pow-operator.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1

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