#112ordered structs (equivalent of `struct A(B)` in rust)

~clover commented · 2 years ago
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right now tuples cast to each other, exactly like arrays do. this is how rust and zig both works. additionally, this behavior also makes @Im-Beast's proposal about allowing field names in tuples impossible, since you could have multiple definitions with different names.

it seems we want to have an ordered struct that

is nominal

can access fields by name or index

an example of such struct could be like Point/Vec3 where there are three components which are ordered, and you may want to have it be a distinct type instead of just "three numbers"

syntax demonstration

struct Vec2 (float, float) let a = Vec2(2.3, 6.2); let b: Vec2 = .(2.3, 6.2); assert a.0 == 2.3; assert b.1 == 6.2; // with textual field names struct Vec3 (x: float, y: float, z: float) let c: Vec3(1, 1, 1); assert c.y == c.1;

then, tuples become almost exclusively for the existence of two values in a loose way, mostly in returning two values from a function. here is an example of a function signature from the compiler that uses this pattern (to be fair, this is in zig and not the language itself)

fn transformAssignmentTarget( t: *Transform, ctx: BlockContext, node: NodeIndex, ) Allocator.Error!?struct { AssignmentTarget, ResultType } {

i believe that Beast and @lino-levan thought that tuples were going to be what this proposal implements.

Milestone: 0.3.0.
~clover changed the status to Todo · 2 years ago