![[Contents]](contents.gif)
Limbo labels are somewhat like C goto statements, except labels can only be used with break and continue statements in for, while and do...while loops, and in case and alt statements. This transfers control to the end of the enclosing block that is labelled.
There are two typical uses of labels in Limbo. One is to allow an inner loop to break or continue to an outer loop. Another is to break to an outer loop from within a case or alt statement.
Consider the following example. One or more options can be passed to a command and parsed:
loop: for(i := 0; i < len in; i++){
case in[i] {
'v' =>
opt |= Verbose;
's' =>
opt |= Suppress;
'o' =>
opt |= OutFile;
* =>
break loop;
}
}
As long as the ith element in the string in is one of the valid options (v, s, or o), procesing continues; the for loop starts the next iteration. At the point that any other character is encountered, processing is termintated by the break loop statement.
If the label is not used with the break, the for loop simply starts the next iteration.
The next example shows how the label can be used to break out of a multi-nested loop:
u := 0;
line := "<A HREF=\"http://www.lucent.com/inferno\">"
URL := "";
outer: for (i := 0; i < len line; i++) {
if (line[i] == '<') {
while (line[++i] != '>') {
if (line[i:i+6] == "A HREF") {
i += 6;
if (line[i] == '=') {
i += 2;
while (line[i] != '"')
URL[u++] = line[i++];
}
}
break outer;
}
}
}