diff --git a/cheatsheet.md b/cheatsheet.md index 41b703f8..d2fb216b 100644 --- a/cheatsheet.md +++ b/cheatsheet.md @@ -665,6 +665,124 @@ copy.width = 99 print(original.width) // still 10 ``` +## Enums + +ChaiScript supports strongly-typed enums using `enum class` (or equivalently `enum struct`), +matching C++ scoped-enum semantics. Values are accessed via `::` syntax and are type-safe — +a plain integer cannot be passed where an enum type is expected. + +### Basic Definition + +``` +enum class Color { Red, Green, Blue } +``` + +Values are auto-numbered starting from 0. Access them with `Color::Red`, `Color::Green`, etc. + +### Explicit Values + +``` +enum class Priority { Low = 10, Medium = 20, High = 30 } +``` + +Auto-numbering continues from the last explicit value: + +``` +enum class Status { Pending, Active = 5, Done } +// Pending = 0, Active = 5, Done = 6 +``` + +### Specifying an Underlying Type + +By default the underlying type is `int`. Use `: type` to choose a different numeric type: + +``` +enum class Flags : char { Read = 1, Write = 2, Execute = 4 } +``` + +The underlying type must be a numeric type registered in ChaiScript. `string` and other +non-numeric types cannot be used. The available underlying types are: + +| Type | Description | +|------|-------------| +| `int` | (default) signed integer | +| `unsigned_int` | unsigned integer | +| `long` | signed long | +| `unsigned_long` | unsigned long | +| `long_long` | signed long long | +| `unsigned_long_long` | unsigned long long | +| `char` | character (8-bit) | +| `wchar_t` | wide character | +| `char16_t` | 16-bit character | +| `char32_t` | 32-bit character | +| `float` | single-precision float | +| `double` | double-precision float | +| `long_double` | extended-precision float | +| `size_t` | unsigned size type | +| `int8_t` | signed 8-bit | +| `int16_t` | signed 16-bit | +| `int32_t` | signed 32-bit | +| `int64_t` | signed 64-bit | +| `uint8_t` | unsigned 8-bit | +| `uint16_t` | unsigned 16-bit | +| `uint32_t` | unsigned 32-bit | + +### `enum struct` Syntax + +`enum struct` is accepted as a synonym for `enum class`, just like in C++: + +``` +enum struct Direction { North, East, South, West } +``` + +### Constructing from a Value + +Each enum type has a constructor that accepts the underlying type. It validates that the +value matches one of the defined enumerators: + +``` +auto c = Color::Color(1) // creates Color::Green +Color::Color(52) // throws: invalid value +``` + +### `to_underlying` + +Convert an enum value back to its underlying numeric type: + +``` +Color::Red.to_underlying() // 0 +Priority::High.to_underlying() // 30 +``` + +### Comparison + +`==` and `!=` are defined for values of the same enum type: + +``` +assert_true(Color::Red == Color::Red) +assert_true(Color::Red != Color::Green) +``` + +### Type-Safe Dispatch + +Functions declared with an enum parameter type reject plain integers: + +``` +def handle(Color c) { /* ... */ } +handle(Color::Red) // ok +handle(42) // throws: dispatch error +``` + +### Using with `switch` + +``` +switch(Color::Green) { + case (Color::Red) { print("red"); break } + case (Color::Green) { print("green"); break } + case (Color::Blue) { print("blue"); break } +} +``` + ## Dynamic Objects All ChaiScript defined types and generic Dynamic_Object support dynamic parameters diff --git a/grammar/chaiscript.ebnf b/grammar/chaiscript.ebnf index 8016f920..d95fe92b 100644 --- a/grammar/chaiscript.ebnf +++ b/grammar/chaiscript.ebnf @@ -18,8 +18,8 @@ /* ---- Top-level ---- */ -statements ::= ( def | try | if | while | class | for - | switch | return | break | continue +statements ::= ( def | try | if | while | class | enum + | for | switch | return | break | continue | equation | block | eol )+ /* ---- Functions ---- */ @@ -57,6 +57,17 @@ class ::= "class" id ( ":" id )? eol* class_block class_block ::= "{" class_statements* "}" class_statements ::= def | var_decl | eol +/* ---- Enums ---- */ + +enum ::= "enum" ( "class" | "struct" ) id ( ":" underlying_type )? + "{" enum_entries? "}" + +enum_entries ::= enum_entry ( "," enum_entry )* + +enum_entry ::= id ( "=" integer )? + +underlying_type ::= id + /* ---- Blocks & flow keywords ---- */ block ::= "{" statements* "}"