GBBopen 1.5 Reference -- with-timeout

with-timeout

with-timeout (seconds timeout-form*) form* => result* [Macro]

Purpose
Bound the time allowed to evaluate forms to seconds, evaluating timeout-forms if the time limit is reached.

Package :portable-threads

Module :portable-threads

Arguments and values

seconds		A number
timeout-forms		An implicit progn of forms to be evaluated if the timed `forms` do not complete before `seconds` seconds have elapsed
forms		An implicit progn of forms to be evaluated
results		The values returned by evaluating the last `form` or the last `timeout-form`

Returns
The values returned by evaluating the last form if completed in less than seconds seconds; otherwise the values returned by evaluating the last timeout-form

Errors
Threads (multiprocessing) is not supported on the Common Lisp implementation. However, with-timeout is also supported on non-threaded SBCL.

Description
If the evaluation of forms does not complete within seconds seconds, execution of forms is terminated and the timeout-forms are evaluated, returning the result of the last timeout-form. The timeout-forms are not evaluated if the forms complete within seconds seconds, in which case the result of the last form is returned.

Examples
Evaluate a simple form, with a one-second time out:

  > (with-timeout (1 ':timed-out) 
       ':did-not-time-out)
  :did-not-time-out
  >

Again, but this time sleep for two seconds to cause a time out:

  > (with-timeout (1 ':timed-out)
       (sleep 2) 
       ':did-not-time-out)
  :timed-out              ; (after 1 second)
  >

Uses of with-timeout can be nested:

  > (with-timeout (1 ':timed-out-outer)
       (with-timeout (2 ':timed-out-inner)
          (sleep 3)
          ':did-not-time-out))
  :timed-out-outer        ; (after 1 second)
  > (with-timeout (2 ':timed-out-outer)
       (with-timeout (1 ':timed-out-inner)
          (sleep 3)
          ':did-not-time-out))
  :timed-out-inner        ; (after 1 second)
  >

The GBBopen Project

with-timeout