pxt-calliope/docs/reference/loops/while.md

44 lines
1.2 KiB
Markdown
Raw Normal View History

2016-03-26 00:47:20 +01:00
# While
2016-04-02 01:22:47 +02:00
Repeat code in a loop while a condition is true.
2016-03-26 00:47:20 +01:00
### @parent blocks/language
Repeat code while a [Boolean](/microbit/reference/types/boolean) `condition` is true.
### ~hide
```
let condition = false
```
### ~
### Block Editor
![](/static/mb/string-0.png)
The while loop has a *condition* that evaluates to a [Boolean](/microbit/reference/types/boolean) value. After the `do` keyword, add the code that you want to run while the `condition` is `true`. The while loop concludes with `end while`.
The condition is tested before any code runs. Which means that if the condition is false, the code inside the loop doesn't execute.
### Example: diagonal line
The following example uses a while loop to make a diagonal line on the LED screen (points `0, 0`, `1, 1`, `2, 2`, `3, 3`, `4, 4`).
// index is set to 4
![](/static/mb/blocks/var-10.png)
// subtract 1 from `index` each time through loop
### Lessons
[rotation animation](/microbit/lessons/rotation-animation)
### See also
[on button pressed](/microbit/reference/input/on-button-pressed), [for](/microbit/reference/loops/for), [if](/microbit/blocks/if), [forever](/microbit/reference/basic/forever)