ref: 88326ef46d597b689b83ec8a44bde60ee8622537
dir: /Loops/README.md/
# Loops
Looping in Limbo is similar to looping in C. Supported loop formats are for, while, and do-while.
## Source
### loops.b:18,23
for(i := 0; i < 10; i++){
if(i % 2 == 0)
continue;
print("%d\n", i * i);
}
A for loop consists of an initialization, qualification, operation, and post-iteration sequence.
Before the loop begins, but before the initial check, `i := 0` is run.
After each loop iteration, `i++` is performed, then `i < 10` is checked.
The `continue` keyword, from the point it is called, skips to the next loop iteration. In this case, `continue` is called if `i` is an even number. If `i` is an odd number, `i²` is printed.
Note that the `continue` keyword does not skip the post-iteration operation.
### loops.b:28,29
while(n)
print("%d\n", n--);
A while loop will check the qualifier for whether to enter another iteration, then, perform its operation. This loop will print the value of `n` in the range [7,1].
Note that in this case the braces are omitted.
### loops.b:33,36
do{
print("%d\n", ++n);
break;
}while(1);
A do-while loop will perform its operation, then check the qualifier for whether to enter another iteration. In this case, the qualifier is a constant which is quantified as a true value, so, this loop would iterate forever.
The `break` keyword interrupts iterative processing. In this case, it terminates the loop immediately after the print on its first iteration.
Note that we reuse the value of `n`, In this case, the incremented value of `n` is printed, as when the preceding loop ends, the value of `n` is 0.
## Demo
; limbo loops.b
; loops
== for
1
9
25
49
81
== while
7
6
5
4
3
2
1
== do
1
;
## Exercises
- Try reversing the ++/-- operators in different places, what happens?
- Try omitting various portions of the for loop syntax, what happens?
- Is `for(;;);` an infinite loop?
- Make the condition for a loop something similar to --n, how many iterations does it run for?