[ruby-core:102530] [Ruby master Feature#17608] Compact and sum in one step

Issue #17608 has been updated by mame (Yusuke Endoh).


I think this is an endless argument. [An idiom "`.compact.max`" is 10x more frequent than "`.compact.sum`"](https://github.com/search?l=Ruby&q=compact.max&type=Code
) in GitHub search. If we introduce `Array#compact_max`, then `#compact_min` and `#compact_minmax` should be also introduced. Next, why don't we need `#compact_max_by`, `#compact_max_by`, and `#compact_minmax_by`? Maybe some people want `#compact_sort_by` eventually.

We have never yet had combination methods `#sort_uniq` and `#zip_map`, which are clearly frequent idioms. You need to prove that `.compact.sum` is really special, e.g., it is a critical performance bottleneck in multiple real-world applications, it is indisputably frequent (like `#filter_map`), it is difficult to work around (like `#flat_map`), etc.

----------------------------------------
Feature #17608: Compact and sum in one step
https://bugs.ruby-lang.org/issues/17608#change-90429

* Author: sawa (Tsuyoshi Sawada)
* Status: Rejected
* Priority: Normal
----------------------------------------
Many use cases of `Array#sum` are preceded with the `compact` method or are followed by a block to ensure the value is addable.

```ruby
a = [1, nil, 2, 3]

a.sum # !> TypeError

a.compact.sum # => 6

a.sum{_1 || 0} # => 6
```

I propose there should be a way to do that in one step. I request either of the following:

A. Change the current behaviour to skip `nil`s.

```ruby
a.sum # => 6
```

B. `Array#filter_sum` method

```ruby
a.filter_sum # => 6
```

C. An option for `Array#sum` 

```ruby
a.sum(compact: true) # => 6
```



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