For in Chapel

Chapel provides several ways to create loops. Here are some basic types of loops.

use IO;

proc main() {
    // The most basic type, with a single condition.
    var i = 1;
    while i <= 3 {
        writeln(i);
        i += 1;
    }

    // A classic initial/condition/after loop.
    for j in 0..#3 {
        writeln(j);
    }

    // Another way of accomplishing the basic "do this
    // N times" iteration is to use a range.
    for i in 0..#3 {
        writeln("range ", i);
    }

    // A loop without a condition will run indefinitely
    // until you break out of the loop or return from
    // the enclosing function.
    while true {
        writeln("loop");
        break;
    }

    // You can also continue to the next iteration of
    // the loop.
    for n in 0..#6 {
        if n % 2 == 0 {
            continue;
        }
        writeln(n);
    }
}

When you run this program, you’ll see:

$ ./for
1
2
3
0
1
2
range 0
range 1
range 2
loop
1
3
5

In Chapel, the for loop is more versatile than in many other languages. It can iterate over ranges, arrays, and other iterable objects. The while loop is used for condition-based looping.

The ..# syntax in Chapel creates a range from 0 to n-1, which is similar to the range-based for loops in the original example.

Chapel doesn’t have a direct equivalent to Go’s for range over an integer, but using a range with ..# achieves the same result.

We’ll see other forms of loops later when we look at iterating over arrays, domains, and other data structures.

Constants in Chapel

If Else in Chapel

Learn X By Example

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For in Chapel