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Feature #18366

Updated by sawa (Tsuyoshi Sawada) over 2 years ago

Some `Enumerable` methods return one or more of the receiver's elements according to the return value of a block it takes. Often, we want such evaluated value rather than the original element. 

 For example, suppose we want to know the character width sufficient to fit all the strings in an array: 

 ```ruby 
 a = ["Hello", "my", "name", "is", "Ruby"] 
 ``` 

 We either have to repeat the evaluation of the block: 

 ```ruby 
 a.max_by(&:length).length # => 5 
 ``` 

 or create a temporal array: 

 ```ruby 
 a.map(&:length).max # => 5 
 ``` 

 both of which seem not to be optimal. 

 I propose to have a method `Enumerator#return_eval` that returns the evaluated value(s) of the block: 

 ```ruby 
 a.max_by.return_eval(&:length) a.max_by.return_value(&:length) # => 5 
 a.min_by.return_eval(&:length) a.min_by.return_value(&:length) # => 2 
 a.minmax_by.return_eval(&:length) a.minmax_by.return_value(&:length) # => [2, 5] 
 ["Ava Davidson", "Benjamin Anderson", "Charlie Baker"] 
 .sort_by.return_eval{_1.split.reverse.join(", .sort_by.return_value{_1.split.reverse.join(", ")}    # => ["Anderson, Benjamin", "Baker, Charlie", "Davidson, Ava"] 
 ``` 

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