(guile.info.gz) Asyncs
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32.2 Asyncs
===========
An async is a pair of one thunk (a parameterless procedure) and a mark.
Setting the mark on an async guarantees that the thunk will be executed
somewhen in the future ("asynchronously"). Setting the mark more than
once is satisfied by one execution of the thunk.
Guile supports two types of asyncs: Normal asyncs and system asyncs.
They differ in that marked system asyncs are executed implicitly as soon
as possible, whereas normal asyncs have to be invoked explicitly.
System asyncs are held in an internal data structure and are maintained
by Guile.
Normal asyncs are created with `async', system asyncs with
`system-async'. They are marked with `async-mark' or
`system-async-mark', respectively.
-- Scheme Procedure: async thunk
-- C Function: scm_async (thunk)
Create a new async for the procedure THUNK.
-- Scheme Procedure: system-async thunk
-- C Function: scm_system_async (thunk)
Create a new async for the procedure THUNK. Also add it to the
system's list of active async objects.
-- Scheme Procedure: async-mark a
-- C Function: scm_async_mark (a)
Mark the async A for future execution.
-- Scheme Procedure: system-async-mark a
-- C Function: scm_system_async_mark (a)
Mark the async A for future execution.
As already mentioned above, system asyncs are executed automatically.
Normal asyncs have to be explicitly invoked by storing one or more of
them into a list and passing them to `run-asyncs'.
-- Scheme Procedure: run-asyncs list_of_a
-- C Function: scm_run_asyncs (list_of_a)
Execute all thunks from the asyncs of the list LIST_OF_A.
Automatic invocation of system asyncs can be temporarily disabled by
calling `mask-signals' and `unmask-signals'. Setting the mark while
async execution is disabled will nevertheless cause the async to run
once execution is enabled again. Please note that calls to these
procedures should always be paired, and they must not be nested, e.g. no
`mask-signals' is allowed if another one is still active.
-- Scheme Procedure: mask-signals
-- C Function: scm_mask_signals ()
Mask signals. The returned value is not specified.
-- Scheme Procedure: unmask-signals
-- C Function: scm_unmask_signals ()
Unmask signals. The returned value is not specified.
-- Scheme Procedure: noop . args
-- C Function: scm_noop (args)
Do nothing. When called without arguments, return `#f', otherwise
return the first argument.
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