*current-thread*

The symbol sys:*current-thread* names a symbol-macro which when executed returns the current thread. Note, despite being called a "variable", this symbol does not have a value. Evaluating the symbol results in the current thread as a return value, but applying boundp to this symbol returns nil and applying symbol-value to it results in an error. (We call it a "variable" because we do not really have a documentation category that fits it otherwise.)

sys:*current-thread* is implemented as a symbol-macro because doing so is much more efficient, getting the value in just several instructions without even needing, on some platforms, a memory reference.

The distinction between thread and process is arcane, but the most important thing is this:

• Thread objects are simple static structures that contain the information used to schedule.
• Process objects are clos instances, allowing the application to define subclasses for whatever purpose.

See also *current-process*. See multiprocessing.htm for more information on multiprocessing.

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This page was not revised from the 8.1 page.
Created 2010.1.21.