From bug-octave-request at bevo dot che dot wisc dot edu Fri Dec 19 19:18:41 2003
Subject: documentation patch for persistent
From: Quentin Spencer <qspencer at ieee dot org>
To: bug-octave at bevo dot che dot wisc dot edu
Date: Fri, 19 Dec 2003 19:18:17 -0600

The following patches add documentation for persistent variables. Please 
feel free to add to this if I missed anything. I'm not an expert on 
texinfo, so I may not have got everything right.


*** src/help.cc.~1.129.~        2003-07-25 22:45:11.000000000 -0500
--- src/help.cc 2003-12-19 18:28:50.000000000 -0600
***************
*** 279,284 ****
--- 279,287 ----
    { "if",
      "Begin an if block.", },

+   { "persistent",
+     "Declare variables as persistent.", },
+
    { "return",
      "Return from a function.", },



*** doc/interpreter/var.txi.~1.18.~     2003-09-09 12:49:13.000000000 -0500
--- doc/interpreter/var.txi     2003-12-19 19:11:09.000000000 -0600
***************
*** 55,60 ****
--- 55,61 ----

   at menu
  * Global Variables::
+ * Persistent Variables::
  * Status of Variables::
  * Summary of Built-in Variables::
  * Defaults from the Environment::
***************
*** 154,159 ****
--- 155,201 ----

   at DOCSTRING(isglobal)

+  at node Persistent Variables
+  at section Persistent Variables
+  at cindex persistent variables
+  at cindex @code{persistent} statement
+  at cindex variables, persistent
+
+ A variable that has been declared  at dfn{persistent} within a function
+ will retain its contents in memory between subsequent calls to the
+ same function. The difference between persistent variables and global
+ variables is that persistent variables are local in scope to a
+ particular function and are not visible elsewhere.
+
+ A variable may be declared persistent using a  at code{persistent}
+ declaration statement.  The following statements are all persistent
+ declarations.
+
+  at example
+  at group
+ persistent a
+ persistent a b
+ persistent c = 2
+ persistent d = 3 e f = 5
+  at end group
+  at end example
+
+ The behavior of persistent variables is equivalent to the behavior of
+ static variables in C. The command  at code{static} in octave is also
+ recognized and is equivalent to  at code{persistent} dot  Unlike global
+ variables, every initialization statement will re-initialize the
+ variable. For example, after executing the following code
+
+  at example
+  at group
+ persistent pvar = 1
+ persistent pvar = 2
+  at end group
+  at end example
+
+  at noindent
+ the value of the persistent variable  at code{pvar} is 2.
+
   at node Status of Variables
   at section Status of Variables




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