While statements

The Language Reference - While Statements

While statements provide a convenient way to generate to write loops that execute a loop as long their condition is true. They have the form while condition then ...statements end, where condition is an argument, similar to one that could be passed to [[goto ... when |Branches]], and statements consist of the code to execute as long as the condition is true.

x: get #30
while not zero then
    x: dec
end

// This code is equivalent to the above, except that the labels are completely private in the former.
x: get #30
begin
    def while_loop:
    goto end_while when zero
    begin
        x: dec
    end
    goto while_loop
    def end_while:
end

If you prefer, you can use do instead of then after the while condition:

x: get #30
while not zero do
    x: dec
end