[ruby-core:106802] [Ruby master Bug#18163] Unclear String documentation of <=> and casecmp methods

Issue #18163 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 2.6: DONTNEED, 2.7: DONTNEED, 3.0: REQUIRED to 2.6: DONTNEED, 2.7: DONTNEED, 3.0: DONE

ruby_3_0 badffc7bee32251e2bea5897dc502b887e7ffa9b merged revision(s) 7f4e86804d426d79807cc038fe4444f7c65f5c4a.

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Bug #18163: Unclear String documentation of <=> and casecmp methods
https://bugs.ruby-lang.org/issues/18163#change-95611

* Author: pvalena (Pavel Valena)
* Status: Closed
* Priority: Normal
* ruby -v: ruby 3.0.2p107 (2021-07-07 revision 0db68f0233) [x86_64-linux]
* Backport: 2.6: DONTNEED, 2.7: DONTNEED, 3.0: DONE
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I have a new student learning Ruby, and there are apparent inconsistencies in Ruby documentation.
The problem appears to be in the order of parameters / variables `self` and `other_string`.

<=>
https://docs.ruby-lang.org/en/3.0.0/String.html#method-i-3C-3D-3E

Firstly it says: 

```
 string <=> other_string → -1, 0, 1, or nil

  -1 if other_string is smaller.

```

I'd expect `'B' <=> 'A'` to result in `-1` since 'B' is smaller. However that's not the case.

```
irb(main):001:0> 'B' <=> 'A'
=> 1

```

casecmp
https://docs.ruby-lang.org/en/3.0.0/String.html#method-i-casecmp

Identical issue, but I think more apparent is with `casecmp`

```
casecmp(other_str) → -1, 0, 1, or nil

  -1 if other_string is smaller.

```

From the description, I expect `other_str` = `'food'` in the following example:

```
'foo'.casecmp('food') # => -1
```

`food` (other_string) is however not `smaller` than `foo`, so I'd expect the result to be `1`.





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