# Behn Examples

Here are a couple of practical examples of using Behn's `%wait` and `%rest` tasks.

## %wait <a href="#wait" id="wait"></a>

Here we'll look at setting a timer by passing Behn a `%wait` task and taking the `%wake` gift it returns when the timer fires.

Below is a thread which will take a `@dr` as its argument and `%pass`es Behn a `%wait` task to fire `@dr` in the future. When the timer fires, it'll then take the `%wake` gift and print it to the terminal along with the time that has elapsed.

`wait.hoon`

```hoon
/-  spider
/+  *strandio
=,  strand=strand:spider
^-  thread:spider
|=  arg=vase
=/  m  (strand ,vase)
^-  form:m
=/  delay=@dr  (need !<((unit @dr) arg))
;<  t1=@da  bind:m  get-time
=/  =task:behn  [%wait (add delay t1)]
=/  =card:agent:gall  [%pass /timer %arvo %b task]
;<  ~  bind:m  (send-raw-card card)
;<  res=(pair wire sign-arvo)  bind:m  take-sign-arvo
?>  ?=([%timer ~] p.res)
?>  ?=([%behn %wake *] q.res)
%-  (slog ~[leaf+"Gift: {<+.q.res>}"])
?~  error.q.res
  ;<  t2=@da  bind:m  get-time
  %-  (slog ~[leaf+"Time elapsed: {<`@dr`(sub t2 t1)>}"])
  (pure:m !>(~))
%-  (slog u.error.q.res)
(pure:m !>(~))
```

Save the thread to `/ted/wait.hoon` and `|commit %base`. Then we can try running the thread with a `@dr` of `~s2`:

```
> -wait ~s2
Gift: [%wake error=~]
Time elapsed: ~s2..0154
```

As you can see, the timer has fired successfully after `~s2` and Behn has given us a `%wake` gift.

## %rest <a href="#rest" id="rest"></a>

Here we'll look at cancelling a previously set timer by passing Behn a `%rest` task.

Below is a variation on the [%wake](#wake) thread. It takes a `@dr` as its argument and sets a timer that far in the future, as before. However, it also sets a second timer twice the `@dr` in the future, and then cancels the first with a `%rest` task. If the `%rest` task succeeds in cancelling the first timer, the `%wake` gift will arrive after double the specified delay.

`rest.hoon`

```hoon
/-  spider
/+  *strandio
=,  strand=strand:spider
^-  thread:spider
|=  arg=vase
=/  m  (strand ,vase)
^-  form:m
=/  delay=@dr  (need !<((unit @dr) arg))
;<  t1=@da  bind:m  get-time
=/  timer1=@da  (add t1 delay)
=/  timer2=@da  (add t1 (mul delay 2))
;<  ~  bind:m  (send-raw-card [%pass /timer %arvo %b %wait timer1])
;<  ~  bind:m  (send-raw-card [%pass /timer %arvo %b %wait timer2])
;<  ~  bind:m  (send-raw-card [%pass /timer %arvo %b %rest timer1])
;<  res=(pair wire sign-arvo)  bind:m  take-sign-arvo
?>  ?=([%timer ~] p.res)
?>  ?=([%behn %wake *] q.res)
%-  (slog ~[leaf+"Gift: {<+.q.res>}"])
?~  error.q.res
  ;<  t2=@da  bind:m  get-time
  %-  (slog ~[leaf+"Time elapsed: {<`@dr`(sub t2 t1)>}"])
  (pure:m !>(~))
%-  (slog u.error.q.res)
(pure:m !>(~))
```

Save the above thread to `/ted/rest.hoon`, and `|commit %base`. Let's try run it with an argument of `~s2`:

```
> -rest ~s2
Gift: [%wake error=~]
Time elapsed: ~s4..00d4
```

As you can see, the timer fired after four seconds, which means the two second timer was successfully cancelled by the `%rest` task.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.urbit.org/urbit-os/kernel/behn/examples.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.