[ruby-core:121798] [Ruby Feature#21300] Suggestion: Method for Array truncation

[ruby-core:121798] [Ruby Feature#21300] Suggestion: Method for Array truncation

[sigsys (Math Ieu) via ruby-core]

Issue #21300 has been reported by sigsys (Math Ieu).

----------------------------------------
Feature #21300: Suggestion: Method for Array truncation
https://bugs.ruby-lang.org/issues/21300

* Author: sigsys (Math Ieu)
* Status: Open
----------------------------------------
`#pop(n)` and `#slice!(...)` can be used for truncation, but they both allocate a new array for the deleted elements (unless you do it one at a time with `#pop()`...), which is not always needed.

I propose adding a `#size=` method for truncating without allocating a new array:

```
a = [10, 20, 30]
a.size = 2
a # [10, 20]
```

Growing the array could be allowed as well...

```
a = [10, 20]
a.size = 4
a # [10, 20, nil, nil]
```




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[ruby-core:121799] [Ruby Feature#21300] Suggestion: Method for Array truncation

[Eregon (Benoit Daloze) via ruby-core]

Issue #21300 has been updated by Eregon (Benoit Daloze).


Using `ary.size =` feels unidiomatic Ruby to me, it feels very low level and not very expressive about the intent (e.g. it's not clear if shrinking or growing).

I don't think pop(n) returning an Array is big overhead, i.e., I don't think there is enough reason to add another Array method for this rarely-needed case.

----------------------------------------
Feature #21300: Suggestion: Method for Array truncation
https://bugs.ruby-lang.org/issues/21300#change-112864

* Author: sigsys (Math Ieu)
* Status: Open
----------------------------------------
`#pop(n)` and `#slice!(...)` can be used for truncation, but they both allocate a new array for the deleted elements (unless you do it one at a time with `#pop()`...), which is not always needed.

I propose adding a `#size=` method for truncating without allocating a new array:

```
a = [10, 20, 30]
a.size = 2
a # [10, 20]
```

Growing the array could be allowed as well...

```
a = [10, 20]
a.size = 4
a # [10, 20, nil, nil]
```




-- 
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