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Add documentation for enum predicate methods #816

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Feb 6, 2025
Merged

Add documentation for enum predicate methods #816

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02ff22a
Update minimum Linux kernel version 2.6.22 (#814)
straight-shoota Jan 14, 2025
c532484
Update enum.md docs
stephannv Feb 2, 2025
7323de0
Fix question methods title size
stephannv Feb 2, 2025
68d873b
Format note
stephannv Feb 2, 2025
915cb37
Improve method usage example
stephannv Feb 2, 2025
7bc69a3
Revert "Update minimum Linux kernel version 2.6.22 (#814)"
straight-shoota Feb 3, 2025
bad4ed7
Fix case ... end
stephannv Feb 3, 2025
aedbcff
Change from question methods to predicate methods
stephannv Feb 5, 2025
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49 changes: 43 additions & 6 deletions docs/syntax_and_semantics/enum.md
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Original file line number Diff line number Diff line change
Expand Up @@ -97,23 +97,60 @@ puts Color.new(10) # => prints "10"

This method is mainly intended to convert integers from C to enums in Crystal.

## Methods
## Question methods

Just like a class or a struct, you can define methods for enums:
An enum automatically defines question methods for each member, using
`String#underscore` for the method name.

!!! note
In the case of regular enums, this compares by equality (`==`). In the case of flags enums, this invokes `includes?`.

For example:

```crystal
enum Color
Red
Green
Blue
end

color = Color::Blue
color.red? # => false
color.blue? # => true

@[Flags]
enum IOMode
Read
Write
Async
end

def red?
self == Color::Red
mode = IOMode::Read | IOMode::Async
mode.read? # => true
mode.write? # => false
mode.async? # => true
```

## Methods

Just like a class or a struct, you can define methods for enums:

```crystal
enum ButtonSize
Sm
Md
Lg

def label
case self
in .sm? then "small"
in .md? then "medium"
in .lg? then "large"
end
end

Color::Red.red? # => true
Color::Blue.red? # => false
ButtonSize::Sm.label # => "small"
ButtonSize::Lg.label # => "large"
```

Class variables are allowed, but instance variables are not.
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8 changes: 4 additions & 4 deletions docs/syntax_and_semantics/platform_support.md
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Expand Up @@ -21,8 +21,8 @@ and drop into *Tier 2*.
| ------ | ----------- | ------------------ | ------- |
| `aarch64-darwin` | Aarch64 macOS<br> (Apple Silicon) | 11+ *(testing only on 14)* | :material-checkbox-marked-circle: tests<br> :material-checkbox-marked-circle: builds |
| `x86_64-darwin` | x64 macOS<br> (Intel) | 11+<br> *(testing only on 13; expected to work on 10.7+)* | :material-checkbox-marked-circle: tests<br> :material-checkbox-marked-circle: builds |
| `x86_64-linux-gnu` | x64 Linux | kernel 4.14+, GNU libc 2.26+<br> *(expected to work on kernel 2.6.18+)* | :material-checkbox-marked-circle: tests<br> :material-checkbox-marked-circle: builds |
| `x86_64-linux-musl` | x64 Linux | kernel 4.14+, MUSL libc 1.2+<br> *(expected to work on kernel 2.6.18+)* | :material-checkbox-marked-circle: tests<br> :material-checkbox-marked-circle: builds |
| `x86_64-linux-gnu` | x64 Linux | kernel 4.14+, GNU libc 2.26+<br> *(expected to work on kernel 2.6.22+)* | :material-checkbox-marked-circle: tests<br> :material-checkbox-marked-circle: builds |
| `x86_64-linux-musl` | x64 Linux | kernel 4.14+, MUSL libc 1.2+<br> *(expected to work on kernel 2.6.22+)* | :material-checkbox-marked-circle: tests<br> :material-checkbox-marked-circle: builds |

***

Expand All @@ -38,8 +38,8 @@ Details are described in the *Comment* column.
| `aarch64-linux-gnu` | Aarch64 Linux | GNU libc 2.26+ | :material-checkbox-marked-circle: tests<br> :material-selection-ellipse: builds |
| `aarch64-linux-musl` | Aarch64 Linux | MUSL libc 1.2+ | :material-checkbox-marked-circle: tests<br> :material-selection-ellipse: builds |
| `arm-linux-gnueabihf` | Aarch32 Linux<br> (hardfloat) | GNU libc 2.26+ | :material-selection-ellipse: tests<br> :material-selection-ellipse: builds |
| `i386-linux-gnu` | x86 Linux | kernel 4.14+, GNU libc 2.26+<br> *(expected to work on kernel 2.6.18+)* | :material-selection-ellipse: tests<br> :material-selection-ellipse: builds |
| `i386-linux-musl` | x86 Linux | kernel 4.14+, MUSL libc 1.2+<br> *(expected to work on kernel 2.6.18+)* | :material-selection-ellipse: tests<br> :material-selection-ellipse: builds |
| `i386-linux-gnu` | x86 Linux | kernel 4.14+, GNU libc 2.26+<br> *(expected to work on kernel 2.6.22+)* | :material-selection-ellipse: tests<br> :material-selection-ellipse: builds |
| `i386-linux-musl` | x86 Linux | kernel 4.14+, MUSL libc 1.2+<br> *(expected to work on kernel 2.6.22+)* | :material-selection-ellipse: tests<br> :material-selection-ellipse: builds |
| `x86_64-openbsd` | x64 OpenBSD | 6+ | :material-selection-ellipse: tests<br> :material-selection-ellipse: builds |
| `x86_64-freebsd` | x64 FreeBSD | 12+ | :material-selection-ellipse: tests<br> :material-selection-ellipse: builds |

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