rfc:user_defined_operator_overloads

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rfc:user_defined_operator_overloads [2021/12/09 07:49] – copy edit jordanrlrfc:user_defined_operator_overloads [2022/01/17 01:16] (current) – closed voting jordanrl
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   * Date: 2021-08-14   * Date: 2021-08-14
   * Author: Jordan LeDoux, jordan.ledoux@gmail.com   * Author: Jordan LeDoux, jordan.ledoux@gmail.com
-  * Status: Under Discussion+  * Status: Declined
   * First Published at: http://wiki.php.net/rfc/user_defined_operator_overloads   * First Published at: http://wiki.php.net/rfc/user_defined_operator_overloads
  
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 This is avoided by allowing the restrictions on operator names to be separated from the restrictions on function names. This is avoided by allowing the restrictions on operator names to be separated from the restrictions on function names.
  
-=== Non-Callable ===+=== Callable ===
  
-Operand implementations cannot be called on an instance of an object the way normal methods can.+Operand implementations can be called on an instance of an object the way normal methods can.
  
 <code php> <code php>
-// These all should result in an error +// These all will work normally 
-$obj->'+'(1, OperandPosition::LeftSide);+$op = '+'; 
 +$callable = [$obj, '+']; 
 + 
 +// Calls on the object variable 
 +$obj->{'+'}(1, OperandPosition::LeftSide); 
 +$obj->$op(1, OperandPosition::LeftSide); 
 +$callable(1, OperandPosition::LeftSide); 
 + 
 +// Calls using call_user_func
 call_user_func([$obj, '+'], 1, OperandPosition::LeftSide); call_user_func([$obj, '+'], 1, OperandPosition::LeftSide);
 +call_user_func($callable, 1, OperandPosition::LeftSide);
 +
 +// This will error since + is not static
 call_user_func('ObjClass::+', 1, OperandPosition::LeftSide); call_user_func('ObjClass::+', 1, OperandPosition::LeftSide);
 +</code>
 +
 +They can be also be directly invoked with a Closure however. This fully supports Reflection, and allows direct calls.
 +
 +<code php>
 +// Manually creating a closure allows a direct function call
 +$closure = Closure::fromCallable([$obj, '+']);
 +$closure(1, OperandPosition::LeftSide);
 +
 +// You can also retrieve the closure through Reflection
 +$closure = (new ReflectionMethod($obj, '+'))->getClosure($obj);
 +$closure(1, OperandPosition::LeftSide);
 +
 +$closure = (new ReflectionObject($obj))->getOperator('+')->getClosure($obj);
 +$closure(1, OperandPosition::LeftSide);
 </code> </code>
  
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 Any return value larger than 0 will be normalized to 1, and any return value smaller than 0 will be normalized to -1. Any return value larger than 0 will be normalized to 1, and any return value smaller than 0 will be normalized to -1.
  
-The $operandPos argument is omitted as it could only be used for evil e.g. implementing different comparison logic depending on which side its on. Instead of passing $operandPos the engine will multiply the result of the call by (-1) where appropriate:+The $operandPos argument is omitted as it could only be used for evil e.g. implementing different comparison logic depending on which side it'on. Instead of passing $operandPos the engine will multiply the result of the call by (-1) where appropriate:
  
 <code php> <code php>
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 These methods need to be updated to ignore the operator methods. Since these are stored internally like any other function on the class entry, they need to be filtered from the results. These methods need to be updated to ignore the operator methods. Since these are stored internally like any other function on the class entry, they need to be filtered from the results.
  
-The reason for removing the operators from this result is because the operator methods are not callable with string literals on the object. Since they cannot be called like a method is, the should be returned with the other methods on a class.+The reason for removing the operators from this result is because the operator methods are not callable with string literals on the object. Since they cannot be called like a method is, they should not be returned with the other methods on a class.
  
 == Adding getOperators(), getOperator(), and hasOperator() == == Adding getOperators(), getOperator(), and hasOperator() ==
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 } }
  
-$result = new Money(5, 'USD') + new Vextor2d(5, 10);+$result = new Money(5, 'USD') + new Vector2d(5, 10);
  
 // Type error, Vector2d can't be used as Money // Type error, Vector2d can't be used as Money
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 // The rest of the extension's do_operation handler // The rest of the extension's do_operation handler
 </code> </code>
 +
 +To further help extensions support this feature, there are two helper functions:
 +
 +<code c>
 +int has_overload = zend_std_has_op_overload(opcode, &zval);
 +
 +zend_function overload_method = zend_std_get_op_overload(opcode, &ce);
 +</code>
 +
 +It is safe to pass any zval pointer to ''zend_std_has_op_overload()'', as it first checks whether or not the ''Z_TYPE_P(zval) == IS_OBJECT'' and returns 0 if it doesn't.
  
 ==== To Opcache ==== ==== To Opcache ====
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 This RFC deals with allowing each class to define its own interaction with operators. However, if overloading the operator itself were desired for the entire application, a different approach would be needed. This is also something that the ''operator'' keyword future proofs against, but is not an intended proposal of this RFC author. This RFC deals with allowing each class to define its own interaction with operators. However, if overloading the operator itself were desired for the entire application, a different approach would be needed. This is also something that the ''operator'' keyword future proofs against, but is not an intended proposal of this RFC author.
  
-===== Proposed Voting Choices ===== +==== Functions for Operators ==== 
-Add limited user-defined operator overloads as describedyes/noA 2/3 vote is required to pass+Having functions for operators may be beneficial when objects which use operator overloads are used in conjunction with functions like ''array_reduce''. For example: 
 + 
 +<code php> 
 +array_reduce($arrOfObjs, +(...)); 
 +</code> 
 + 
 +These could be polyfilled in PHP currently: 
 + 
 +<code php> 
 +array_reduce($arrOfObjs, fn ($a, $b) => ($a + $b)); 
 +</code> 
 + 
 +==== Query Builder Improvements ==== 
 +With some additional improvements, it's possible that operator overloads could provide some very useful tools for things such as query builders: 
 + 
 +<code php> 
 +$qb->select(Product::class)->where(Price::class < 50); 
 +</code> 
 + 
 +==== Enum Return Type For <=> ==== 
 + 
 +Returning an enum for the <=> would be preferable for two reasons. 
 + 
 +  - It allows the function to return an equivalent of 'uncomparable' (where all variations are false) 
 +  - It is easier to read and understand the behavior in code, while integer values often require a moment to remember the meaning 
 + 
 +This is listed as future scope because there is a separate RFC which covers this feature: https://wiki.php.net/rfc/sorting_enum 
 + 
 +It is listed as a separate RFC because it is something that could be delivered whether or not this RFC passes.
  
 ===== Patches and Tests ===== ===== Patches and Tests =====
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   - a link to the language specification section (if any)   - a link to the language specification section (if any)
  
-===== References =====+===== Proposed Voting Choices ===== 
 +Add limited user-defined operator overloads as described: yes/no. A 2/3 vote is required to pass.  
 + 
 +===== Vote ===== 
 + 
 +Voting started 2022-01-03 at 00:15 UTC and will end 2022-01-17 at 00:15 UTC.
  
 +<doodle title="Adopt user defined operator overloads as described?" auth="jordanrl" voteType="single" closed="true">
 +   * Yes
 +   * No
 +</doodle>
  
 ===== Changelog ===== ===== Changelog =====
rfc/user_defined_operator_overloads.1639036167.txt.gz · Last modified: 2021/12/09 07:49 by jordanrl