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Mutex: Difference between revisions
→{{header|Racket}}
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t = res_thread()
t.start()</lang>
=={{header|Racket}}==
Racket has semaphores which can be used as mutexes in the usual way. With other language features this can be used to implement new features -- for example, here is how we would implement a protected-by-a-mutex function:
<lang Racket>(define foo
(let ([sema (make-semaphore 1)])
(lambda (x)
(dynamic-wind (λ() (semaphore-wait sema))
(λ() (... do something ...))
(λ() (semaphore-post sema))))))</lang>
and it is now easy to turn this into a macro for definitions of such functions:
<lang Racket>(define-syntax-rule (define/atomic (name arg ...) E ...)
(define name
(let ([sema (make-semaphore 1)])
(lambda (arg ...)
(dynamic-wind ( () (semaphore-wait sema))
( () E ...)
( () (semaphore-post sema)))))))
;; this does the same as the above now:
(define/atomic (foo x)
(... do something ...))</lang>
But more than just linguistic features, Racket has many additional synchronization tools in its VM. Some notable examples: OS semaphore for use with OS threads, green threads, lightweight OS threads, and heavyweight OS threads, synchronization channels, thread mailboxes, CML-style event handling, generic synchronizeable event objects, non-blocking IO, etc, etc.
=={{header|Ruby}}==
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