UPdate.
This commit is contained in:
@@ -0,0 +1,284 @@
|
||||
{# retoor <retoor@molodetz.nl> #}
|
||||
{% extends 'page.html' %}
|
||||
|
||||
{% set page_title = "Fibers" %}
|
||||
{% set breadcrumb = [{"url": "language/index.html", "title": "Language"}, {"title": "Fibers"}] %}
|
||||
{% set prev_page = {"url": "language/control-flow.html", "title": "Control Flow"} %}
|
||||
{% set next_page = {"url": "language/modules.html", "title": "Modules"} %}
|
||||
|
||||
{% block article %}
|
||||
<h1>Fibers</h1>
|
||||
|
||||
<p>Fibers are Wren's mechanism for cooperative concurrency. They are lightweight threads of execution that you explicitly control. Unlike OS threads, only one fiber runs at a time, and switching between them is explicit.</p>
|
||||
|
||||
<h2>Creating Fibers</h2>
|
||||
<p>Create a fiber with <code>Fiber.new</code>:</p>
|
||||
<pre><code>var fiber = Fiber.new {
|
||||
System.print("Inside fiber")
|
||||
}</code></pre>
|
||||
|
||||
<p>The fiber does not run immediately. It is suspended until you start it.</p>
|
||||
|
||||
<h2>Running Fibers</h2>
|
||||
|
||||
<h3>call()</h3>
|
||||
<p>Start a fiber and wait for it to complete or yield:</p>
|
||||
<pre><code>var fiber = Fiber.new {
|
||||
System.print("Running")
|
||||
}
|
||||
|
||||
fiber.call() // Prints "Running"</code></pre>
|
||||
|
||||
<h3>try()</h3>
|
||||
<p>Start a fiber and catch any runtime errors:</p>
|
||||
<pre><code>var fiber = Fiber.new {
|
||||
Fiber.abort("Something went wrong")
|
||||
}
|
||||
|
||||
var error = fiber.try()
|
||||
System.print("Error: %(error)") // Error: Something went wrong</code></pre>
|
||||
|
||||
<h2>Yielding</h2>
|
||||
<p>Fibers can pause execution and return control to the caller:</p>
|
||||
<pre><code>var fiber = Fiber.new {
|
||||
System.print("First")
|
||||
Fiber.yield()
|
||||
System.print("Second")
|
||||
Fiber.yield()
|
||||
System.print("Third")
|
||||
}
|
||||
|
||||
fiber.call() // Prints "First"
|
||||
fiber.call() // Prints "Second"
|
||||
fiber.call() // Prints "Third"</code></pre>
|
||||
|
||||
<h3>Yielding Values</h3>
|
||||
<pre><code>var counter = Fiber.new {
|
||||
Fiber.yield(1)
|
||||
Fiber.yield(2)
|
||||
Fiber.yield(3)
|
||||
}
|
||||
|
||||
System.print(counter.call()) // 1
|
||||
System.print(counter.call()) // 2
|
||||
System.print(counter.call()) // 3</code></pre>
|
||||
|
||||
<h3>Passing Values In</h3>
|
||||
<pre><code>var adder = Fiber.new {
|
||||
var total = 0
|
||||
while (true) {
|
||||
var value = Fiber.yield(total)
|
||||
total = total + value
|
||||
}
|
||||
}
|
||||
|
||||
adder.call() // Start the fiber
|
||||
System.print(adder.call(5)) // 5
|
||||
System.print(adder.call(10)) // 15
|
||||
System.print(adder.call(3)) // 18</code></pre>
|
||||
|
||||
<h2>Fiber State</h2>
|
||||
<p>Check the state of a fiber:</p>
|
||||
<pre><code>var fiber = Fiber.new {
|
||||
Fiber.yield()
|
||||
}
|
||||
|
||||
System.print(fiber.isDone) // false
|
||||
|
||||
fiber.call()
|
||||
System.print(fiber.isDone) // false (yielded)
|
||||
|
||||
fiber.call()
|
||||
System.print(fiber.isDone) // true (completed)</code></pre>
|
||||
|
||||
<h2>Error Handling</h2>
|
||||
<p>Fibers can abort with an error:</p>
|
||||
<pre><code>Fiber.abort("Error message")</code></pre>
|
||||
|
||||
<p>Use <code>try()</code> to catch errors:</p>
|
||||
<pre><code>var fiber = Fiber.new {
|
||||
var x = 1 / 0 // Will cause infinity, not error
|
||||
[1, 2, 3][10] // This will cause an error
|
||||
}
|
||||
|
||||
var error = fiber.try()
|
||||
if (error != null) {
|
||||
System.print("Caught: %(error)")
|
||||
}</code></pre>
|
||||
|
||||
<h2>Current Fiber</h2>
|
||||
<p>Get the currently executing fiber:</p>
|
||||
<pre><code>var current = Fiber.current
|
||||
System.print(current) // Fiber instance</code></pre>
|
||||
|
||||
<h2>Generator Pattern</h2>
|
||||
<p>Fibers naturally implement generators:</p>
|
||||
<pre><code>var range = Fn.new { |start, end|
|
||||
return Fiber.new {
|
||||
var i = start
|
||||
while (i <= end) {
|
||||
Fiber.yield(i)
|
||||
i = i + 1
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
var nums = range.call(1, 5)
|
||||
while (!nums.isDone) {
|
||||
var value = nums.call()
|
||||
if (value != null) System.print(value)
|
||||
}</code></pre>
|
||||
|
||||
<h2>Coroutine Pattern</h2>
|
||||
<p>Two fibers can communicate back and forth:</p>
|
||||
<pre><code>var producer = Fiber.new {
|
||||
for (i in 1..5) {
|
||||
System.print("Producing %(i)")
|
||||
Fiber.yield(i)
|
||||
}
|
||||
}
|
||||
|
||||
var consumer = Fiber.new {
|
||||
while (!producer.isDone) {
|
||||
var value = producer.call()
|
||||
if (value != null) {
|
||||
System.print("Consuming %(value)")
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
consumer.call()</code></pre>
|
||||
|
||||
<h2>Async Operations with Scheduler</h2>
|
||||
<p>Wren-CLI uses fibers for async I/O. The scheduler suspends fibers during I/O and resumes them when the operation completes:</p>
|
||||
<pre><code>import "timer" for Timer
|
||||
|
||||
System.print("Before sleep")
|
||||
Timer.sleep(1000) // Fiber suspends here
|
||||
System.print("After sleep")</code></pre>
|
||||
|
||||
<p>The scheduler pattern internally looks like:</p>
|
||||
<pre><code>import "scheduler" for Scheduler
|
||||
|
||||
Scheduler.await_ {
|
||||
Timer.sleep_(1000, Fiber.current)
|
||||
}</code></pre>
|
||||
|
||||
<h2>Fiber Methods</h2>
|
||||
|
||||
<h3>Static Methods</h3>
|
||||
<table>
|
||||
<tr>
|
||||
<th>Method</th>
|
||||
<th>Description</th>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>Fiber.new { block }</code></td>
|
||||
<td>Create a new fiber</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>Fiber.current</code></td>
|
||||
<td>Get the current fiber</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>Fiber.yield()</code></td>
|
||||
<td>Pause and return null</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>Fiber.yield(value)</code></td>
|
||||
<td>Pause and return value</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>Fiber.abort(message)</code></td>
|
||||
<td>Abort with error</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>Fiber.suspend()</code></td>
|
||||
<td>Suspend the current fiber</td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h3>Instance Methods</h3>
|
||||
<table>
|
||||
<tr>
|
||||
<th>Method</th>
|
||||
<th>Description</th>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.call()</code></td>
|
||||
<td>Run fiber, wait for yield/complete</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.call(value)</code></td>
|
||||
<td>Run with value passed to yield</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.try()</code></td>
|
||||
<td>Run and catch errors</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.isDone</code></td>
|
||||
<td>True if completed</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.error</code></td>
|
||||
<td>Error message if aborted</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.transfer()</code></td>
|
||||
<td>Switch to this fiber</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.transfer(value)</code></td>
|
||||
<td>Switch with value</td>
|
||||
</tr>
|
||||
<tr>
|
||||
<td><code>fiber.transferError(msg)</code></td>
|
||||
<td>Switch and raise error</td>
|
||||
</tr>
|
||||
</table>
|
||||
|
||||
<h2>Transfer vs Call</h2>
|
||||
<p><code>call()</code> maintains a call stack and returns when the fiber yields:</p>
|
||||
<pre><code>var a = Fiber.new {
|
||||
System.print("a: before yield")
|
||||
Fiber.yield()
|
||||
System.print("a: after yield")
|
||||
}
|
||||
|
||||
a.call()
|
||||
System.print("back in main")
|
||||
a.call()
|
||||
|
||||
// Output:
|
||||
// a: before yield
|
||||
// back in main
|
||||
// a: after yield</code></pre>
|
||||
|
||||
<p><code>transfer()</code> does not maintain a call stack:</p>
|
||||
<pre><code>var main = Fiber.current
|
||||
var a = null
|
||||
var b = null
|
||||
|
||||
a = Fiber.new {
|
||||
System.print("in a")
|
||||
b.transfer()
|
||||
System.print("back in a")
|
||||
main.transfer()
|
||||
}
|
||||
|
||||
b = Fiber.new {
|
||||
System.print("in b")
|
||||
a.transfer()
|
||||
System.print("back in b")
|
||||
}
|
||||
|
||||
a.transfer()
|
||||
System.print("done")
|
||||
|
||||
// Output:
|
||||
// in a
|
||||
// in b
|
||||
// back in a
|
||||
// done</code></pre>
|
||||
{% endblock %}
|
||||
Reference in New Issue
Block a user