box-extra: box utilities

8.12

box-extra: box utilities🔗ℹ

Extra utilities for working with boxes.

1 Reference🔗ℹ

value
box-update-strategy/c : (or/c 'busy 'semaphore)
value
box-update-proc/c : (-> (-> any/c any/c) any/c)

procedure
(make-box-update-proc b [strategy]) → box-update-proc/c
b : box?
strategy : box-update-strategy/c = 'semaphore

Returns a procedure that may be used to update the value within b using the given retry strategy.

The 'semaphore strategy synchronizes retrying threads using a semaphore. See box-update/semaphore! for details.

The 'busy strategy retries without any sort of backoff. See box-update/busy! for details.

Examples:

> (require box-extra)
> (define b (box 0))
> (define update-b! (make-box-update-proc b))
> (update-b! add1)
1
> (unbox b)
1

procedure
(box-update/busy! b proc) → any/c
b : box?
proc : (-> any/c any/c)

Updates b by applying proc to its current value. When box-cas! is fails, it retries immediately. Returns the value that was last put in the box.

Prefer box-update/semaphore! over this function. Only use this function if you’re sure that multiple threads won’t attempt to update b concurrently.

procedure
(box-update/semaphore! b sema proc) → any/c
  b : box?
  sema : semaphore?
  proc : (-> any/c any/c)

Updates b by applying proc to its current value. When box-cas! fails, it waits on sema before retrying. Returns the value that was last put in the box.

The sema argument must have an initial count of 1.

Examples:

> (require box-extra)
> (define b (box 0))
> (define sema (make-semaphore 1))
> (define thds
    (list
     (thread (λ () (box-update/semaphore! b sema add1)))
     (thread (λ () (box-update/semaphore! b sema add1)))))
> (for-each thread-wait thds)
> (unbox b)
2

1.1 Unsafe API🔗ℹ

(require box-extra/unsafe)

package: box-extra-lib

procedure
(make-unsafe-box-update-proc b [strategy]) → box-update-proc/c
  b : box?
  strategy : box-update-strategy/c = 'semaphore
procedure
(unsafe-box-update/busy! b proc) → any/c
  b : box?
  proc : (-> any/c any/c)
procedure
(unsafe-box-update/semaphore! b sema proc) → any/c
  b : box?
  sema : semaphore?
  proc : (-> any/c any/c)

Unsafe variants of make-box-update-proc, box-update/busy! and box-update/semaphore!, respectively.