while

Summary#

while repeats its body as long as the condition is true, checked before each pass — so a condition that is false at the start means the body never runs. The condition must be a bool.

Signature#

while (<bool>) { … }

Description#

while, foreach, or for — which loop?#

Use while when you do not know up front how many passes you need — consuming until something is exhausted, converging on a value. When you are walking a collection, foreach says it better; when you are counting, so does for.

int TimesToHalve(decimal amount, decimal limit) {
  var steps = 0;
  var current = amount;
  while (current > limit) {
    current = current / 2;
    steps += 1;
  }
  return steps;
}

Advance the condition, or it never ends#

The body must move the condition towards false. A while whose condition never changes is an infinite loop, and the platform will not save you from it — it will simply run until it is stopped. Make the thing the condition reads the thing the body changes, and keep them close enough to see together.

How do I stop part-way through?#

break leaves the loop; continue skips to the next check. See break / continue.

int CountUpTo(int limit) {
  var i = 0;
  while (true) {
    i += 1;
    if (i >= limit) { break; }     // the exit is explicit, and easy to find
  }
  return i;
}

See also#

• foreach — walking a collection
• for — a counted loop
• break / continue — leaving a loop, or skipping a pass