# enum

const expect = @import("std").testing.expect;
const mem = @import("std").mem;

// Declare an enum.
const Type = enum {
    ok,
    not_ok,
};

// Declare a specific enum field.
const c = Type.ok;

// If you want access to the ordinal value of an enum, you
// can specify the tag type.
const Value = enum(u2) {
    zero,
    one,
    two,
};
// Now you can cast between u2 and Value.
// The ordinal value starts from 0, counting up by 1 from the previous member.
test "enum ordinal value" {
    try expect(@intFromEnum(Value.zero) == 0);
    try expect(@intFromEnum(Value.one) == 1);
    try expect(@intFromEnum(Value.two) == 2);
}

// You can override the ordinal value for an enum.
const Value2 = enum(u32) {
    hundred = 100,
    thousand = 1000,
    million = 1000000,
};
test "set enum ordinal value" {
    try expect(@intFromEnum(Value2.hundred) == 100);
    try expect(@intFromEnum(Value2.thousand) == 1000);
    try expect(@intFromEnum(Value2.million) == 1000000);
}

// You can also override only some values.
const Value3 = enum(u4) {
    a,
    b = 8,
    c,
    d = 4,
    e,
};
test "enum implicit ordinal values and overridden values" {
    try expect(@intFromEnum(Value3.a) == 0);
    try expect(@intFromEnum(Value3.b) == 8);
    try expect(@intFromEnum(Value3.c) == 9);
    try expect(@intFromEnum(Value3.d) == 4);
    try expect(@intFromEnum(Value3.e) == 5);
}

// Enums can have methods, the same as structs and unions.
// Enum methods are not special, they are only namespaced
// functions that you can call with dot syntax.
const Suit = enum {
    clubs,
    spades,
    diamonds,
    hearts,

    pub fn isClubs(self: Suit) bool {
        return self == Suit.clubs;
    }
};
test "enum method" {
    const p = Suit.spades;
    try expect(!p.isClubs());
}

// An enum can be switched upon.
const Foo = enum {
    string,
    number,
    none,
};
test "enum switch" {
    const p = Foo.number;
    const what_is_it = switch (p) {
        Foo.string => "this is a string",
        Foo.number => "this is a number",
        Foo.none => "this is a none",
    };
    try expect(mem.eql(u8, what_is_it, "this is a number"));
}

// @typeInfo can be used to access the integer tag type of an enum.
const Small = enum {
    one,
    two,
    three,
    four,
};
test "std.meta.Tag" {
    try expect(@typeInfo(Small).@"enum".tag_type == u2);
}

// @typeInfo tells us the field count and the fields names:
test "@typeInfo" {
    try expect(@typeInfo(Small).@"enum".fields.len == 4);
    try expect(mem.eql(u8, @typeInfo(Small).@"enum".fields[1].name, "two"));
}

// @tagName gives a [:0]const u8 representation of an enum value:
test "@tagName" {
    try expect(mem.eql(u8, @tagName(Small.three), "three"));
}

$ zig test test_enums.zig
1/8 test_enums.test.enum ordinal value...OK
2/8 test_enums.test.set enum ordinal value...OK
3/8 test_enums.test.enum implicit ordinal values and overridden values...OK
4/8 test_enums.test.enum method...OK
5/8 test_enums.test.enum switch...OK
6/8 test_enums.test.std.meta.Tag...OK
7/8 test_enums.test.@typeInfo...OK
8/8 test_enums.test.@tagName...OK
All 8 tests passed.

const Foo = enum { a, b, c };
export fn entry(foo: Foo) void {
    _ = foo;
}

$ zig build-obj enum_export_error.zig -target x86_64-linux
/home/andy/dev/zig/doc/langref/enum_export_error.zig:2:17: error: parameter of type 'enum_export_error.Foo' not allowed in function with calling convention 'x86_64_sysv'
export fn entry(foo: Foo) void {
                ^~~~~~~~
/home/andy/dev/zig/doc/langref/enum_export_error.zig:2:17: note: enum tag type 'u2' is not extern compatible
/home/andy/dev/zig/doc/langref/enum_export_error.zig:2:17: note: only integers with 0, 8, 16, 32, 64 and 128 bits are extern compatible
/home/andy/dev/zig/doc/langref/enum_export_error.zig:1:13: note: enum declared here
const Foo = enum { a, b, c };
            ^~~~~~~~~~~~~~~~
referenced by:
    root: /home/andy/dev/zig/lib/std/start.zig:3:22
    comptime: /home/andy/dev/zig/lib/std/start.zig:31:9
    2 reference(s) hidden; use '-freference-trace=4' to see all references

const Foo = enum(c_int) { a, b, c };
export fn entry(foo: Foo) void {
    _ = foo;
}

$ zig build-obj enum_export.zig

const std = @import("std");
const expect = std.testing.expect;

const Color = enum {
    auto,
    off,
    on,
};

test "enum literals" {
    const color1: Color = .auto;
    const color2 = Color.auto;
    try expect(color1 == color2);
}

test "switch using enum literals" {
    const color = Color.on;
    const result = switch (color) {
        .auto => false,
        .on => true,
        .off => false,
    };
    try expect(result);
}

$ zig test test_enum_literals.zig
1/2 test_enum_literals.test.enum literals...OK
2/2 test_enum_literals.test.switch using enum literals...OK
All 2 tests passed.

const std = @import("std");
const expect = std.testing.expect;

const Number = enum(u8) {
    one,
    two,
    three,
    _,
};

test "switch on non-exhaustive enum" {
    const number = Number.one;
    const result = switch (number) {
        .one => true,
        .two, .three => false,
        _ => false,
    };
    try expect(result);
    const is_one = switch (number) {
        .one => true,
        else => false,
    };
    try expect(is_one);
}

$ zig test test_switch_non-exhaustive.zig
1/1 test_switch_non-exhaustive.test.switch on non-exhaustive enum...OK
All 1 tests passed.