Type Function and anytype

Explain
9

I mostly share your confusion.

Doing generic data types via ‘fn (T: type, ...) type {’ was one of Zig features I was able to understand very quickly. But anytype is another kind of beast.

It seems anytype is not a type at all (like u32, type(!!!) etc). It looks more like an instruction to the compiler - “expect argument of any type and do monomorphization for each actual type encountered in a program”.

I can do generic polymorphic addition by two ways.

with anytype, like this:

const std = @import("std");

fn add1(a: anytype, b: @TypeOf(a)) @TypeOf(a) {
    return a + b;
}

pub fn main() void {

    const x: f32 = 1;
    const y: f32 = 2;
    std.debug.print("{}\n", .{add1(x,y)});

    const j: u32 = 1;
    const k: u32 = 2;
    std.debug.print("{}\n", .{add1(j,k)});
}

We have two monomorphized versions:

zig-lang/anytype$ nm 1 | grep add1
000000000103c0d0 t 1.add1__anon_3427
000000000103c2b0 t 1.add1__anon_3429

with type type:

onst std = @import("std");

fn add2(T: type, a: T, b: T) T {
    return a + b;
}

pub fn main() void {

    const x: f32 = 1;
    const y: f32 = 2;
    std.debug.print("{}\n", .{add2(@TypeOf(x),x,y)});

    const j: u32 = 1;
    const k: u32 = 2;
    std.debug.print("{}\n", .{add2(@TypeOf(j),j,k)});
}

Again, we have two versions of the function:

zig-lang/anytype$ nm 2 | grep add2
000000000103c0d0 t 2.add2__anon_3427
000000000103c2b0 t 2.add2__anon_3429

What is the difference?
In the second case we indicate arguments’ type explicitly, in the first one it is done automatically, I think so. Correct me, if am wrong.

As to type type and anytype mix - I think they are orthogonal to each other.
Just because anytype is not a name of a type.

anytype is for “parametric polymorphism”, type type is for generic data structures, a sort of that.