Concurrent utility for Scheme
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Concurrent library for Scheme

This library is extracted from Sagittarius Scheme for portability. The changes made on this library would be merged into Sagittarius itself and vice versa.


See (util concurrent)


This library requires following SRFIs:

For R7RS, this is required:

Tested implementations

Unfortunately, not all R6RS implementations support SRFI-18. So only the following implementations are currently supported:

  • Sagittarius
  • Guile 2.0.11

NOTE: on Guile, some of the tests may faile due to the bug of thread-sleep!

The following R7RS implementations are also tested:

  • Chibi Scheme (0.7.3) : works partially
  • Gauche (0.9.4)

Why should you use this?

Using raw thread, mutex and condition variables often causes dead lock or other problems. This library provides 4 components which reduce manual operation of them and possibly decrease the possiblity of multi threading related issues.

Shared queue

(util concurrent shared-queue)

Inter-thread communication sometimes required if you need write multi thread programming. This component makes it easier instead of using mutex and condition variables.

Thread pool

(util concurrent thread-pool)

Limiting number of threads might be required by your environment. This component re-use managed threads.

Future and executor

(util concurrent future) and (util concurrent executor)

Future makes you to write asynchronouse program easier. Using simple future is equivalent with making a thread, starting the thread and joining the thread. Combination of executor and future provides easier resource management.


  • Supporting Racket.
  • Supporting R7RS implementations which supports SRFI-18.

Copyright and lincense

Copyright 2016 Takashi Kato. Code released under the BSD-style license. See COPYING.