rfc:list_assoc_unique

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rfc:list_assoc_unique [2022/12/01 14:24] – ilutovrfc:list_assoc_unique [2022/12/01 18:01] – ilutov
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 ===== Introduction ===== ===== Introduction =====
  
-The <php>array_unique</php> function allows getting all unique values of a given array. Unfortunately, PHP has multiple+The <php>array_unique()</php> function allows getting all unique values of a given array. Unfortunately, PHP has multiple
 definitions of equality and thus uniqueness. The most obvious one (i.e. <php>$a === $b</php>) is not supported by definitions of equality and thus uniqueness. The most obvious one (i.e. <php>$a === $b</php>) is not supported by
-<php>array_unique</php>.+<php>array_unique()</php>.
  
 This RFC proposes adding two new functions, <php>List\unique()</php> and <php>Assoc\unique()</php> as alternatives This RFC proposes adding two new functions, <php>List\unique()</php> and <php>Assoc\unique()</php> as alternatives
 using strict equality (<php>===</php>) semantics, the former discarding and the latter preserving keys. using strict equality (<php>===</php>) semantics, the former discarding and the latter preserving keys.
  
-<php>+<code php>
 List\unique([1, 2, 3, 1, '2', 3.0, new Foo, ['bar']]) List\unique([1, 2, 3, 1, '2', 3.0, new Foo, ['bar']])
-> [1, 2, 3, '2', 3.0, Foo, ['bar']]+// > [1, 2, 3, '2', 3.0, Foo, ['bar']]
  
 Assoc\unique(['foo' => 'foo', 'bar' => 'bar', 'baz' => 'foo']) Assoc\unique(['foo' => 'foo', 'bar' => 'bar', 'baz' => 'foo'])
-> ['foo' => 'foo', 'bar' => 'bar'] +// > ['foo' => 'foo', 'bar' => 'bar'] 
-</php>+</code>
  
 ===== Proposal ===== ===== Proposal =====
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 Removing duplicates from arrays is a common use case provided by many programming languages. PHPs <php>array_unique()</php> Removing duplicates from arrays is a common use case provided by many programming languages. PHPs <php>array_unique()</php>
 has been there for [[https://github.com/php/php-src/commit/99f151f1bde0483944767cf0ed49d3270f61d326|~23 years]]. has been there for [[https://github.com/php/php-src/commit/99f151f1bde0483944767cf0ed49d3270f61d326|~23 years]].
-However, PHP has multiple definitions of equality, four in particular supported by <php>array_unique</php>:+However, PHP has multiple definitions of equality, four in particular supported by <php>array_unique()</php>:
  
   * <php>SORT_STRING</php> - Converts values to strings and compares with <php><</php>/<php>==</php>/<php>></php>   * <php>SORT_STRING</php> - Converts values to strings and compares with <php><</php>/<php>==</php>/<php>></php>
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   * <php>SORT_LOCALE_STRING</php> - Converts values to strings and compares with ''strcoll''   * <php>SORT_LOCALE_STRING</php> - Converts values to strings and compares with ''strcoll''
  
-Arguably, the most straight forward of those in terms of coercion is <php>SORT_STRING</php>. However, none of these +Internally, <php>array_unique()</php> sorts the array to avoid comparing each value with every other value which would 
-options support arrays and objects, and all of them are subject to subtle coercion issues. Additionally, coercion can +scale badly. For this reason, the second parameter <php>$flags</php> accepts the same <php>SORT_*</php> options as 
-lead to warnings that are likely undesirable, as the fact that these values are coerced for comparison is an +<php>sort()</php> function and friends. 
-implementation detail.+ 
 +None of these options support arrays and objects, and other primitive types are subject to subtle coercion issues. 
 +Additionally, coercion can lead to warnings that are likely undesirable, as the fact that these values are coerced for 
 +comparison is an implementation detail.
  
 ==== Keys ==== ==== Keys ====
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 ===== Alternative approaches ===== ===== Alternative approaches =====
  
-Previously, adding a new parameter to <php>array_unique()</php> was discussed. The discussion has revealed that most +Previously, adding a new <php>ARRAY_UNIQUE_IDENTICAL</php> constant that can be passed to <php>array_unique()</php>s <php>$flag</php> 
-people would prefer a new function over fixing the existing function with a new parameter that might be more difficult +parameter was discussed. The discussion has revealed that most people would prefer a new function over extending <php>array_unique()</php> 
-to discover.+with a flag that might be more difficult to discover.
  
 ===== Vote ===== ===== Vote =====
rfc/list_assoc_unique.txt · Last modified: 2022/12/01 18:19 by ilutov

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