5f7a8e5301
* update yotta defaults for 16kb devices * refactor deprecated blocks * updates for button events * update button events * update refference * update docs * update docs * update button event blocks * update docs * update block id
84 lines
2.3 KiB
Markdown
84 lines
2.3 KiB
Markdown
# forever
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Keep running part of a program
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[in the background](/reference/control/in-background).
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```sig
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basic.forever(() => {
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})
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```
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You can have part of a program continuously by placing it in an **forever** loop. The **forever** loop will _yield_ to the other code in your program though, allowing that code to have time to run when needs to.
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### ~ reminder
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#### Event-based loops
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Both the **forever** loop and the **every** loop are _event-based_ loops where the code inside is run as part of a function. These are different from the [for](/blocks/loops/for) and [while](/blocks/loops/while) loops. Those are loops are part of the programming language and can have [break](/blocks/loops/break) and [continue](/blocks/loops/continue) statements in them.
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You can NOT use **break** or **continue** in either a **forever** loop or an **every** loop.
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### ~
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## Examples
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### Example: compass
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The following example constantly checks the
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[compass heading](/reference/input/compass-heading)
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and updates the screen with the direction.
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```blocks
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let degrees = 0
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basic.forever(() => {
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degrees = input.compassHeading()
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if (degrees < 45) {
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basic.showString("N")
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} else if (degrees < 135) {
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basic.showString("E")
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} else if (degrees < 225) {
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basic.showString("S")
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} else if (degrees < 315) {
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basic.showString("W")
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} else {
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basic.showString("N")
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}
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})
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```
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### Example: counter
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The following example keeps showing the [number](/types/number) stored in a global variable.
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When you press button `A`, the number gets bigger.
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You can use a program like this to count things with your @boardname@.
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```blocks
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let num = 0
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basic.forever(() => {
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basic.showNumber(num)
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})
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input.onButtonEvent(Button.A, input.buttonEventClick(), () => {
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num = num + 1
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})
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```
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## Competing for the LED screen
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If different parts of a program are each trying
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to show something on the LED screen at the same time,
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you may get unexpected results.
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Try this on your @boardname@:
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```blocks
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basic.forever(() => {
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basic.showNumber(6789)
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})
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input.onButtonEvent(Button.A, input.buttonEventClick(), () => {
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basic.showNumber(2)
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})
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```
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## See also
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[while](/blocks/loops/while), [in background](/reference/control/in-background), [every](/reference/loops/every-interval)
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