Loops and Blocks and Labels

Explain
1

Just a funny I noticed:

What do you think the output of this program would be:

const std = @import("std");
pub fn main() !void {
	var i: u32 = 0;
	while (i < 6) : (i += 1) b: {
		std.debug.print("BLOCK\n", .{});
		if (i >= 3) break :b;

		std.debug.print("LOOP\n", .{});
	} else {
		std.debug.print("ELSE\n", .{});
	}
}

In other words, does breaking out of the then block break out of the loop?

(obviously you can just run the program I am just curious about everyone’s intuition)

4 Likes
2

Isn’t the break :b; effectively functioning as a continue?

I would expect 6x BLOCK, the first 3 of which followed by LOOP (until the break/continue takes effect) and then the ELSE

4 Likes
3

It’s the same as if it said continue, right? Don’t show this to andrew, he might remove the keyword for redundancy then :rofl:

15 Likes
4

Lets quickly flag the post as inappropriate

4 Likes
5

I think it makes sense to remove continue, even though this keyword has been used to implement state machines in switch statements.

6

Oh no not another cursed language feature… I love it.

7

:slight_smile: as long as we can rename break to goto…

1 Like
8

This is exactly how I “continue” from inline for loops.

Example

3 Likes
9

The semantics are vastly different: goto refers to jumping to a label, whereas Zig’s break refers to leaving the code block where the label is located.

10

Obviously the solution is to change the block’s label location to the end of the block.

{
    do();
    if (cond) goto :label;
    domore();
} :label
1 Like
11

omg… i can’t read this. while...else...

12

OR, hear me out, make this work:

var i: u32 = 0;
block: {
	std.debug.print("{d}\n", .{i});
	if (i < 10)
		continue :block;
}

so that the continue makes it go back to the beginning of the block.

And remove for and while in its favour :upside_down_face:

/j

3 Likes