[Nullabillity]

How do you express the difference between None and Some(None) in Zig?

[anonymoushn]

I've found that types like these normally come up in generic contexts, so the code I'm writing only usually deals with one layer of Option or Result until I get to the bit where I'm actually using the value and find out I have to write "try try foo();". That said, I think this sort of thing will do it:

  const std = @import("std");
  fn some(x: anytype) ?@TypeOf(x) {
    return x;
  }
  fn print_my_guy(maybe_maybe_x: ??u32) void {
    if(maybe_maybe_x) |maybe_x| {
      if (maybe_x) |x| {
        std.debug.print("that's Some(Some({d})) {any}\n", .{x, maybe_maybe_x});
      } else {
        std.debug.print("that's Some(None) {any}\n", .{maybe_maybe_x});
      }
    } else {
      std.debug.print("that's None {any}\n", .{maybe_maybe_x});
    }
  }
  pub fn main() void {
    const a: ??u32 = 5;
    const b: ??u32 = null;
    const c: ??u32 = some(@as(?u32, null));
    print_my_guy(a);
    print_my_guy(b);
    print_my_guy(c);
  }

[bmacho]

What about

  const std = @import("std") ;
  const print = std.debug.print ;
  
  pub fn main() void {
  
    const simple_none : ?u8 = null ;
  
    const double_optional_none : ??u8 = null ;
  
    const double_optional_some_none : ??u8 = simple_none ;

    print("none equals some none: {}", .{ double_optional_none == double_optional_some_none });
    // prints none equals some none: false
  
  }