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Anonymous Structs

The struct type may be omitted from a struct literal. These literals may coerce to other struct types.

test "anonymous struct literal" {
const Point = struct { x: i32, y: i32 };

var pt: Point = .{
.x = 13,
.y = 67,
};
try expect(pt.x == 13);
try expect(pt.y == 67);
}

Anonymous structs may be completely anonymous i.e. without being coerced to another struct type.

test "fully anonymous struct" {
try dump(.{
.int = @as(u32, 1234),
.float = @as(f64, 12.34),
.b = true,
.s = "hi",
});
}

fn dump(args: anytype) !void {
try expect(args.int == 1234);
try expect(args.float == 12.34);
try expect(args.b);
try expect(args.s[0] == 'h');
try expect(args.s[1] == 'i');
}

Anonymous structs without field names may be created and are referred to as tuples. These have many of the properties that arrays do; tuples can be iterated over, indexed, can be used with the ++ and ** operators, and have a len field. Internally, these have numbered field names starting at "0", which may be accessed with the special syntax @"0" which acts as an escape for the syntax - things inside @"" are always recognised as identifiers.

An inline loop must be used to iterate over the tuple here, as the type of each tuple field may differ.

test "tuple" {
const values = .{
@as(u32, 1234),
@as(f64, 12.34),
true,
"hi",
} ++ .{false} ** 2;
try expect(values[0] == 1234);
try expect(values[4] == false);
inline for (values, 0..) |v, i| {
if (i != 2) continue;
try expect(v);
}
try expect(values.len == 6);
try expect(values.@"3"[0] == 'h');
}