async_let_fibonacci.swift

// RUN: %target-run-simple-swift( -target %target-swift-5.1-abi-triple -parse-as-library)

// REQUIRES: executable_test
// REQUIRES: concurrency
// UNSUPPORTED: freestanding

// rdar://76038845
// REQUIRES: concurrency_runtime
// UNSUPPORTED: back_deployment_runtime

func fib(_ n:Int)->Int{
varfirst=0
varsecond=1
for_in0..<n {
lettemp= first
 first = second
 second = temp + first
}
return first
}

@available(SwiftStdlib 5.1,*)
func asyncFib(_ n:Int)async->Int{
if n ==0 || n ==1{
return n
}

asyncletfirst=awaitasyncFib(n-2)
asyncletsecond=awaitasyncFib(n-1)

 // Sleep a random amount of time waiting on the result producing a result.
try!awaitTask.sleep(nanoseconds:UInt64.random(in:0..<100)*1_000_000)

letresult=await first + second

 // Sleep a random amount of time before producing a result.
try!awaitTask.sleep(nanoseconds:UInt64.random(in:0..<100)*1_000_000)

return result
}

@available(SwiftStdlib 5.1,*)
func runFibonacci(_ n:Int)async{
letresult=awaitasyncFib(n)

print("")
print("Async fib = \(result), sequential fib = \(fib(n))")
assert(result ==fib(n))
}

@available(SwiftStdlib 5.1,*)
@mainstructMain{
staticfunc main()async{
awaitrunFibonacci(10)
}
}