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Labelled Blocks

Blocks in Zig are expressions and can be given labels, which are used to yield values. Here, we are using a label called blk. Blocks yield values, meaning they can be used in place of a value. The value of an empty block {} is a value of the type void.

test "labelled blocks" {
const count = blk: {
var sum: u32 = 0;
var i: u32 = 0;
while (i < 10) : (i += 1) sum += i;
break :blk sum;
try expect(count == 45);
try expect(@TypeOf(count) == u32);

This can be seen as being equivalent to C's i++.

blk: {
const tmp = i;
i += 1;
break :blk tmp;