defvar-nonbindable

Arguments: symbol &optional initial-value-form documentation-string

This macro acts like a defvar, with the additional function of flagging symbol so that it cannot be lambda-bound. This means all references to symbol's value are to (sys:global-symbol-value 'symbol).

Here is an example showing the error signaled when there is an attempt to bind a non-bindable variable.

cl-user(1): (defvar-nonbindable *foo*)
*foo*
cl-user(2): (setq *foo* 10)
10
cl-user(3): (let ((*foo* 20)) *foo*)
Error: Cannot bind *foo* -- it is an unbindable symbol.
  [condition type: program-error]

Restart actions (select using :continue):
 0: Prompt for a new variable name.
 1: Return to Top Level (an "abort" restart).
 2: Abort entirely from this (lisp) process.
[1c] cl-user(4): 

See smp.htm and multiprocessing.htm for more information on this macro and on multiprocessing.

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This page was not revised from the 10.0 page.
Created 2019.8.20.