Proposal: bounded while loops

[nittdeniz]

Proposal: Bounded while Loop

Introduce a bounded while loop syntax that limits the number of iterations a loop can perform.

The proposed syntax allows specifying a maximum iteration count directly in the loop declaration:

while[n](condition){
    // body
}

If the loop iterates more than n times, the runtime throws an exception (e.g., CounterExceededException). This helps guard against unintended infinite loops while keeping the code concise and readable.

---

Motivation

When implementing traversal algorithms (e.g., linked lists, graph traversal, or chained structures), loops often follow a pattern similar to:

while (node is not null) {
    // do something
    node = node?.Next;
}

However, bugs in the data structure (e.g., accidental cycles) may lead to unintended infinite loops.

You can mitigate this by introducing a manual iteration counter:

const int limit = 1_000;
var iCounter = 0;

while( condition ){
  if( iCounter++ >= limit ) throw new Exception("Whoops");
  
  // actual stuff
}

[Richiban]

I very much doubt that the language would introduce a construct for such a niche use case when there's a perfectly good way of doing it already.

Also, these sorts of features tend to disappear in a cloud of disagreements about how exactly it should work and how (if at all) it should be customisable. Your idea of a built-in counter might work for some scenarios but you'll quickly find someone saying "I'm using a bounded while loop but under certain conditions this iteration shouldn't count" etc. That's why it's a much better idea that you simply maintain the count yourself so you can put the exact rules on it that you want.

[nittdeniz]

I realise indeed this can be arranged way tidier. Is there a way to delete this post?

[CyrusNajmabadi]

Just mark your post as answered with the 'tidier way' you envision.