* [ruby-core:105607] [Ruby master Bug#18247] weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence`
@ 2021-10-08 15:38 lxxxvi
2022-03-30 23:05 ` [ruby-core:108127] " jeremyevans0 (Jeremy Evans)
0 siblings, 1 reply; 2+ messages in thread
From: lxxxvi @ 2021-10-08 15:38 UTC (permalink / raw)
To: ruby-core
Issue #18247 has been reported by lxxxvi (Mario Schüttel).
----------------------------------------
Bug #18247: weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence`
https://bugs.ruby-lang.org/issues/18247
* Author: lxxxvi (Mario Schüttel)
* Status: Open
* Priority: Normal
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
There are weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence`.
Particularly most results with negative steps are weird. For example:
```ruby
@array = [0, 1, 2, 3, 4, 5]
@array.slice((2..).step(-1)) # => [2, 1, 0]
@array.slice((2..).step(-2)) # => [2, 0]
@array.slice((2..).step(-3)) # => [2]
@array.slice((2..).step(-4)) # => [0] # ??? I'd have expected [2]
@array.slice((-3..).step(-1)) # => [3, 2, 1, 0]
@array.slice((-3..).step(-2)) # => [3, 1]
@array.slice((-3..).step(-3)) # => [3, 0]
@array.slice((-3..).step(-4)) # => [3]
@array.slice((-3..).step(-5)) # => [0] # ??? I'd have expected [3]
```
Have a look at these examples with "beginless" ranges and negative steps.
Particularly the ones exluding the end value (`...`) seem wrong:
```ruby
@array = [0, 1, 2, 3, 4, 5]
## end with zero index
@array.slice((..0).step(-1)) # => [5, 4, 3, 2, 1, 0]
@array.slice((...0).step(-1)) # => [5, 4, 3, 2, 1, 0]
@array.slice((..0).step(-2)) # => [5, 3, 1]
@array.slice((...0).step(-2)) # => [5, 3, 1]
@array.slice((..0).step(-10)) # => [0]
@array.slice((...0).step(-10)) # => [0]
## end with positive index
@array.slice((..3).step(-1)) # => [5, 4, 3]
@array.slice((...3).step(-1)) # => [5, 4, 3]
@array.slice((..3).step(-2)) # => [5, 3]
@array.slice((...3).step(-2)) # => [5, 3]
@array.slice((..3).step(-10)) # => [3]
@array.slice((...3).step(-10)) # => [3]
## end with negative index
@array.slice((..-2).step(-1)) # => [5, 4]
@array.slice((...-2).step(-1)) # => [5, 4]
@array.slice((..-2).step(-2)) # => [5]
@array.slice((...-2).step(-2)) # => [5]
@array.slice((..-2).step(-10)) # => [4]
@array.slice((...-2).step(-10)) # => [4]
```
Finally, some examples where the range is "inverted".
Particularly, the results for the ones excluding the end value (`...`) look strange.
But all examples seem weird, but I might not understand the concept of arithmetic sequence in depth.
```ruby
@array = [0, 1, 2, 3, 4, 5]
# start and end with positive index
@array.slice((3..1).step(-1)) # => [3, 2, 1]
@array.slice((3...1).step(-1)) # => [2, 1]
@array.slice((3..1).step(-2)) # => [3, 1]
@array.slice((3...1).step(-2)) # => [2]
@array.slice((3..1).step(-10)) # => [1]
@array.slice((3...1).step(-10)) # => [1]
# start with negative index, end with positive index
@array.slice((-2..1).step(-1)) # => [4, 3, 2, 1]
@array.slice((-2...1).step(-1)) # => [3, 2, 1]
@array.slice((-2..1).step(-2)) # => [4, 2]
@array.slice((-2...1).step(-2)) # => [3, 1]
@array.slice((-2..1).step(-10)) # => [1]
@array.slice((-2...1).step(-10)) # => [1]
# start with positive index, end with negative index
@array.slice((4..-4).step(-1)) # => [4, 3, 2]
@array.slice((4...-4).step(-1)) # => [3, 2]
@array.slice((4..-4).step(-2)) # => [4, 2]
@array.slice((4...-4).step(-2)) # => [3]
@array.slice((4..-4).step(-10)) # => [2]
@array.slice((4...-4).step(-10)) # => [2]
# start with negative index, end with negative index
@array.slice((-2..-4).step(-1)) # => [4, 3, 2]
@array.slice((-2...-4).step(-1)) # => [3, 2]
@array.slice((-2..-4).step(-2)) # => [4, 2]
@array.slice((-2...-4).step(-2)) # => [3]
@array.slice((-2..-4).step(-10)) # => [2]
@array.slice((-2...-4).step(-10)) # => [2]
```
--
https://bugs.ruby-lang.org/
^ permalink raw reply [flat|nested] 2+ messages in thread
* [ruby-core:108127] [Ruby master Bug#18247] weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence`
2021-10-08 15:38 [ruby-core:105607] [Ruby master Bug#18247] weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence` lxxxvi
@ 2022-03-30 23:05 ` jeremyevans0 (Jeremy Evans)
0 siblings, 0 replies; 2+ messages in thread
From: jeremyevans0 (Jeremy Evans) @ 2022-03-30 23:05 UTC (permalink / raw)
To: ruby-core
Issue #18247 has been updated by jeremyevans0 (Jeremy Evans).
This is still an issue in the master branch. I've submitted a pull request to fix it: https://github.com/ruby/ruby/pull/5739
----------------------------------------
Bug #18247: weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence`
https://bugs.ruby-lang.org/issues/18247#change-97101
* Author: lxxxvi (Mario Schüttel)
* Status: Open
* Priority: Normal
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
There are weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence`.
Particularly most results with negative steps are weird. For example:
```ruby
@array = [0, 1, 2, 3, 4, 5]
@array.slice((2..).step(-1)) # => [2, 1, 0]
@array.slice((2..).step(-2)) # => [2, 0]
@array.slice((2..).step(-3)) # => [2]
@array.slice((2..).step(-4)) # => [0] # ??? I'd have expected [2]
@array.slice((-3..).step(-1)) # => [3, 2, 1, 0]
@array.slice((-3..).step(-2)) # => [3, 1]
@array.slice((-3..).step(-3)) # => [3, 0]
@array.slice((-3..).step(-4)) # => [3]
@array.slice((-3..).step(-5)) # => [0] # ??? I'd have expected [3]
```
Have a look at these examples with "beginless" ranges and negative steps.
Particularly the ones exluding the end value (`...`) seem wrong:
```ruby
@array = [0, 1, 2, 3, 4, 5]
## end with zero index
@array.slice((..0).step(-1)) # => [5, 4, 3, 2, 1, 0]
@array.slice((...0).step(-1)) # => [5, 4, 3, 2, 1, 0]
@array.slice((..0).step(-2)) # => [5, 3, 1]
@array.slice((...0).step(-2)) # => [5, 3, 1]
@array.slice((..0).step(-10)) # => [0]
@array.slice((...0).step(-10)) # => [0]
## end with positive index
@array.slice((..3).step(-1)) # => [5, 4, 3]
@array.slice((...3).step(-1)) # => [5, 4, 3]
@array.slice((..3).step(-2)) # => [5, 3]
@array.slice((...3).step(-2)) # => [5, 3]
@array.slice((..3).step(-10)) # => [3]
@array.slice((...3).step(-10)) # => [3]
## end with negative index
@array.slice((..-2).step(-1)) # => [5, 4]
@array.slice((...-2).step(-1)) # => [5, 4]
@array.slice((..-2).step(-2)) # => [5]
@array.slice((...-2).step(-2)) # => [5]
@array.slice((..-2).step(-10)) # => [4]
@array.slice((...-2).step(-10)) # => [4]
```
Finally, some examples where the range is "inverted".
Particularly, the results for the ones excluding the end value (`...`) look strange.
But all examples seem weird, but I might not understand the concept of arithmetic sequence in depth.
```ruby
@array = [0, 1, 2, 3, 4, 5]
# start and end with positive index
@array.slice((3..1).step(-1)) # => [3, 2, 1]
@array.slice((3...1).step(-1)) # => [2, 1]
@array.slice((3..1).step(-2)) # => [3, 1]
@array.slice((3...1).step(-2)) # => [2]
@array.slice((3..1).step(-10)) # => [1]
@array.slice((3...1).step(-10)) # => [1]
# start with negative index, end with positive index
@array.slice((-2..1).step(-1)) # => [4, 3, 2, 1]
@array.slice((-2...1).step(-1)) # => [3, 2, 1]
@array.slice((-2..1).step(-2)) # => [4, 2]
@array.slice((-2...1).step(-2)) # => [3, 1]
@array.slice((-2..1).step(-10)) # => [1]
@array.slice((-2...1).step(-10)) # => [1]
# start with positive index, end with negative index
@array.slice((4..-4).step(-1)) # => [4, 3, 2]
@array.slice((4...-4).step(-1)) # => [3, 2]
@array.slice((4..-4).step(-2)) # => [4, 2]
@array.slice((4...-4).step(-2)) # => [3]
@array.slice((4..-4).step(-10)) # => [2]
@array.slice((4...-4).step(-10)) # => [2]
# start with negative index, end with negative index
@array.slice((-2..-4).step(-1)) # => [4, 3, 2]
@array.slice((-2...-4).step(-1)) # => [3, 2]
@array.slice((-2..-4).step(-2)) # => [4, 2]
@array.slice((-2...-4).step(-2)) # => [3]
@array.slice((-2..-4).step(-10)) # => [2]
@array.slice((-2...-4).step(-10)) # => [2]
```
Found while writing specs for this method in https://github.com/ruby/spec/pull/857
--
https://bugs.ruby-lang.org/
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2021-10-08 15:38 [ruby-core:105607] [Ruby master Bug#18247] weird results for `Array#slice` or `Array#[]` with argument of type `Enumerator::ArithmeticSequence` lxxxvi
2022-03-30 23:05 ` [ruby-core:108127] " jeremyevans0 (Jeremy Evans)
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