[ruby-core:102494] [Ruby master Feature#17608] Compact and sum in one step

Issue #17608 has been updated by sawa (Tsuyoshi Sawada).


ko1 (Koichi Sasada) wrote in #note-11:
> Can you count on your app or your observation?
> 
> ```
> ko1@aluminium:~$ gem-codesearch 'compact\.sum' | wc -l
> 75
> ```
> 
> not so many cases in gem-codesearch.

I searched on my company's private repository (the `***` in the following was replaced by the repository name):

https://github.com/search?q=org%3A**********+compact.sum&type=Code

and got 94 results. The search itself may match not only exactly `compact.sum` but also strings like `compact_sum`, so I checked through manually, and all of them were `compact.sum` or a variant of it, like `&.compact&.sum`.

When I switch to all results on GitHub:

https://github.com/search?q=compact.sum&type=Code

it says 70,041, but this time, it includes strings like `compact_sum`. I am not sure how many of them are genuine `compact.sum`, but I believe there are many.

You presented the result on gems, but my guess is that `sum` is a relatively newly introduced method, and so gems tend to avoid `sum` in the first place to make them compatible with old Rubies, hence, gems are biased as data source for this purpose.

And please don't forget that, besides `compact.sum`, code fragments like `sum{_1 || 0}` are also relevant use cases.


----------------------------------------
Feature #17608: Compact and sum in one step
https://bugs.ruby-lang.org/issues/17608#change-90388

* 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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