[ruby-core:99428] [Ruby master Feature#17097] `map_min`, `map_max`

[sawadatsuyoshi@gmail.com]

Issue #17097 has been updated by sawa (Tsuyoshi Sawada).


I do not understand why the proposal has to be extended to all other `Enumerable` methods.

My point is semantic. I do not see many use cases where I am interested in the element that is related to the min/max value but am not interested in the min/max value.

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Feature #17097: `map_min`, `map_max`
https://bugs.ruby-lang.org/issues/17097#change-86880

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
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`min`, `min_by`, `max`, `max_by` return the element that leads to the minimum or the maximum value, but I think it is as, or even more, frequent that we are interested in the minimum or the maximum value itself rather than the element. For example, to get the length of the longest string in an array, we do:

```ruby
%w[aa b cccc dd].max_by(&:length).length # => 4
%w[aa b cccc dd].map(&:length).max # => 4
```

I propose to have methods that return the minimum or the maximum value. Temporarily calling them `map_min`, `map_max`, they should work like this:

```ruby
%w[aa b cccc dd].map_max(&:length) # => 4
```

`map_min`, `map_max` are implementation-centered names, so perhaps better names should replace them, just like `yield_self` was replaced by `then`.



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