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< article >
< h1 > scheduler</ h1 >
< p > The < code > scheduler</ code > module manages the async event loop and fiber scheduling. It is the foundation for all async operations in Wren-CLI.</ p >
< pre >< code > import "scheduler" for Scheduler</ code ></ pre >
< h2 > Scheduler Class</ h2 >
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< h3 > Scheduler</ h3 >
< p > Async fiber scheduler</ p >
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< h3 > Static Methods</ h3 >
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< span class = "method-name" > Scheduler.await_</ span > (< span class = "param" > block</ span > ) → < span class = "type" > any</ span >
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< p > Suspends the current fiber until an async operation completes. Used internally by modules to implement async operations.</ p >
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< li >< span class = "param-name" > block</ span > < span class = "param-type" > (Fn)</ span > - Block that initiates the async operation</ li >
< li >< span class = "returns" > Returns:</ span > Result of the async operation</ li >
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< pre >< code > var result = Scheduler.await_ {
Timer.sleep_(1000, Fiber.current)
}</ code ></ pre >
< div class = "method-signature" >
< span class = "method-name" > Scheduler.resume_</ span > (< span class = "param" > fiber</ span > )
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< p > Resumes a suspended fiber. Used by native code to wake up fibers when async operations complete.</ p >
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< span class = "method-name" > Scheduler.resume_</ span > (< span class = "param" > fiber</ span > , < span class = "param" > value</ span > )
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< p > Resumes a fiber with a result value.</ p >
< h2 > How Async Works</ h2 >
< p > Wren-CLI uses an event loop (libuv) for non-blocking I/O. Here is how async operations work:</ p >
< ol >
< li > A Wren fiber calls an async method (e.g., < code > Http.get</ code > )</ li >
< li > The method starts a native async operation and suspends the fiber</ li >
< li > The event loop continues processing other events</ li >
< li > When the operation completes, the fiber is resumed with the result</ li >
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< h3 > Under the Hood</ h3 >
< pre >< code > // How Timer.sleep works internally
class Timer {
static sleep(ms) {
return Scheduler.await_ {
Timer.sleep_(ms, Fiber.current)
}
}
foreign static sleep_(ms, fiber)
}</ code ></ pre >
< h2 > Examples</ h2 >
< h3 > Sequential vs Parallel</ h3 >
< p > Operations are sequential by default:</ p >
< pre >< code > import "http" for Http
// These run one after another (sequential)
var r1 = Http.get("https://api.example.com/1")
var r2 = Http.get("https://api.example.com/2")
var r3 = Http.get("https://api.example.com/3")</ code ></ pre >
< p > For parallel operations, use multiple fibers:</ p >
< pre >< code > import "http" for Http
var fibers = [
Fiber.new { Http.get("https://api.example.com/1") },
Fiber.new { Http.get("https://api.example.com/2") },
Fiber.new { Http.get("https://api.example.com/3") }
]
// Start all fibers
for (f in fibers) f.call()
// Results are already available when fibers complete</ code ></ pre >
< div class = "admonition note" >
< div class = "admonition-title" > Note</ div >
< p > The scheduler is used internally by modules. Most user code does not need to interact with it directly. Use higher-level modules like < code > timer</ code > , < code > http</ code > , and < code > io</ code > instead.</ p >
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< div class = "admonition tip" >
< div class = "admonition-title" > Tip</ div >
< p > Async operations in Wren-CLI are cooperative, not preemptive. A fiber runs until it explicitly yields or calls an async operation.</ p >
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