mlld/docs/src/atoms/control-flow/while.md

mlld: llm scripting language

---
id: while
title: While Loops
brief: Bounded iteration with done/continue control
category: control-flow
tags: [iteration, loops]
related: [for-arrow]
related-code: [interpreter/eval/while.ts]
updated: 2026-01-05
---

Bounded iteration with `while`.

```mlld
exe @countdown(n) = when [
  @n <= 0 => done "finished"
  * => continue (@n - 1)
]

var @result = 5 | while(10) @countdown
```

**Control keywords:**
- `done @value` - Terminate, return value
- `done` - Terminate, return current state
- `continue @value` - Next iteration with new state
- `continue` - Next iteration with current state

**While context** (`@mx.while`):
- `iteration` - Current iteration (1-based)
- `limit` - Configured cap
- `active` - true when inside while

**With pacing:**

```mlld
var @result = @initial | while(100, 1s) @processor  >> 1s between iterations
```