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static local variables

From: John W. Eaton
Subject: static local variables
Date: Fri, 21 Mar 1997 10:31:04 -0600

On 21-Mar-1997, Peter Bruhn <address@hidden> wrote:

| is there some way to have local variables keep their values, after the
| function has been ended and restarted?

Currently, the only way to do this is by using global variables.

| I would like to have this, because I have a lot of sub-functions programmed
| by different people. And I do not want to insert global variables into the
| main-function whenever a sub-function is changed.

You don't need to declare the variables global in the main function.
For example, this function keeps track of the number of times it is

  function f ()
    global f_static_ncalls;
    if (! exist ("f_static_ncalls"))
      f_static_ncalls = 0;
    ## ...

Using a name like FCN_static_FOO helps to avoid name clashses with
real global variables.

Also, it is necessary to use call exist() to decide when to initialize
the variable.  Writing

  global f_static_ncalls = 0;

*should* work to initialize the variable just once, but it doesn't.
This is a bug, and should eventually be fixed.

Finally, I realize that this is not really the Right Thing, so the
PROJECTS file contains the following entry:

  * Make it possible to have `static' variables inside functions that
    retain their values across calls.

Perhaps this will be added in the next release.  Maybe sooner, if
someone contributes the code.  :-)



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