rfc:raising_zero_to_power_of_negative_number

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rfc:raising_zero_to_power_of_negative_number [2024/01/11 21:20] – jorg_sowarfc:raising_zero_to_power_of_negative_number [2024/04/21 00:06] (current) – Changed status to accepted jorg_sowa
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   * Date: 2024-01-11   * Date: 2024-01-11
   * Author: Jorg Sowa <jorg.sowa@gmail.com>   * Author: Jorg Sowa <jorg.sowa@gmail.com>
-  * Status: Draft+  * Status: Accepted
   * First Published at: http://wiki.php.net/rfc/raising_zero_to_power_of_negative_number   * First Published at: http://wiki.php.net/rfc/raising_zero_to_power_of_negative_number
  
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 Raising a number to the power of a negative number is equivalent to taking the reciprocal of the number raised to the positive opposite of the power. Raising a number to the power of a negative number is equivalent to taking the reciprocal of the number raised to the positive opposite of the power.
  
-If we raise the number zero to the power of a negative number we end up with the one divided by zero, which gives an undefined result. Currently in PHP, such operation results in `INF`, while explicit division by zero gives a DivisionByZeroError.+If we raise the number zero to the power of a negative number we end up with the one divided by zero, which gives an undefined result. Currently in PHP, such operation results in <php>INF</php>, while explicit division by zero gives a <php>DivisionByZeroError</php>.
  
 <code php> <code php>
 var_dump(0 ** -1); //float(INF) var_dump(0 ** -1); //float(INF)
 +var_dump(0 ** -1.1); //float(INF)
  
 var_dump(pow(0, -1)); //float(INF) var_dump(pow(0, -1)); //float(INF)
 +var_dump(pow(0, -1.1)); //float(INF)
  
 var_dump(1 / 0); //DivisionByZeroError: Division by zero var_dump(1 / 0); //DivisionByZeroError: Division by zero
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 ===== Proposal ===== ===== Proposal =====
-The RFC proposes to change the behavior of this operation to match the division by zero operation. In the next minor version such an operation will throw a Deprecation notice, and for the major version, this operation will throw DivisionByZeroError.+The RFC proposes to change the behavior of this operation to match the division by zero operation. In the next minor version raising a number to the power of a negative number will throw a Deprecation, and in the major version, this operation will throw DivisionByZeroError. 
 + 
 +<code php> 
 +//PHP 8.4 
 +var_dump(0 ** -1); //Deprecated: Zero raised to a negative power is deprecated 
 +var_dump(0 ** -1.1); //Deprecated: Zero raised to a negative power is deprecated 
 +  
 +var_dump(pow(0, -1)); //Deprecated: Zero raised to a negative power is deprecated 
 +var_dump(pow(0, -1.1)); //Deprecated: Zero raised to a negative power is deprecated 
 +  
 +var_dump(1 / 0); //DivisionByZeroError: Division by zero 
 +</code> 
 + 
 + 
 +<code php> 
 +//PHP 9.0 
 +var_dump(0 ** -1); //DivisionByZeroError: Zero cannot be raised to a negative power 
 +var_dump(0 ** -1.1); //DivisionByZeroError: Zero cannot be raised to a negative power 
 +  
 +var_dump(pow(0, -1)); //DivisionByZeroError: Zero cannot be raised to a negative power 
 +var_dump(pow(0, -1.1)); //DivisionByZeroError: Zero cannot be raised to a negative power 
 +  
 +var_dump(1 / 0); //DivisionByZeroError: Division by zero 
 +</code> 
 + 
 +To provide a way to compute the numbers according to the IEEE 754 rules, the RFC proposes adding the function <php>fpow</php> similarly to the function <php>fdiv</php> that exists for the division operation, and <php>fmod</php> for the module operation for floating numbers. 
 + 
 +<code php> 
 +//PHP 8.4 
 +var_dump(fpow(0, -1)); //float(INF) 
 +var_dump(fpow(0, -1.1)); //float(INF) 
 +</code>
  
 ===== Backward Incompatible Changes ===== ===== Backward Incompatible Changes =====
-This change will break all code including raising the zero number to a negative power.+This change will break code including raising the zero number to a negative power. Such cases may keep their current behavior by using the new <php>fpow</php> function.
  
 ===== Proposed PHP Version(s) ===== ===== Proposed PHP Version(s) =====
 Deprecation Notice in the next minor PHP version 8.4. Deprecation Notice in the next minor PHP version 8.4.
  
-Throwing DivisionByZeroError in the next major PHP version: 9.0.+Function <php>fpow</php> in the next minor PHP version 8.4. 
 + 
 +Throwing <php>DivisionByZeroError</php> in the next major PHP version: 9.0.
  
 ===== Proposed Voting Choices ===== ===== Proposed Voting Choices =====
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 As per the voting RFC, a yes/no vote with a 2/3 majority is needed for this proposal to be accepted. As per the voting RFC, a yes/no vote with a 2/3 majority is needed for this proposal to be accepted.
  
-Voting started 2024-x-x and closed 2024-x-x. +Voting started on 2024-04-05 and will end on 2024-04-20 00:00 GMT. 
 + 
 +<doodle title="RFC: Raising zero to the power of negative number" auth="jorg_sowa" voteType="single" closed="false" closeon="2024-04-20T00:00:00Z"> 
 +   * Yes 
 +   * No 
 +</doodle>
  
 ===== Implementation ===== ===== Implementation =====
-https://github.com/jorgsowa/php-src/pull/11+https://github.com/php/php-src/pull/13128 (without fpow yet)
  
 The implementation is based on Ilija Tovilo's PoC: The implementation is based on Ilija Tovilo's PoC:
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 ===== References ===== ===== References =====
 Issue GH-8015: https://github.com/php/php-src/issues/8015 Issue GH-8015: https://github.com/php/php-src/issues/8015
 +RFC Division by zero: https://wiki.php.net/rfc/engine_warnings
  
rfc/raising_zero_to_power_of_negative_number.1705008003.txt.gz · Last modified: 2024/01/11 21:20 by jorg_sowa

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