Store And Recall Look-Up Paths; Recall Look-Up Path - Texas Instruments TI-89 Developer's Manual

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variables to automatically change. Care must be taken when VarRecall or
VarStore are bypassed by reading or writing directly to any variable using the
low-level symbol table routines. The file system uses VarStore and VarRecall.
13.3.2.1.

Store and Recall Look-up Paths

There are two types of folders: user folders and local (temporary) folders. There
is always a current user folder which can be selected on the mode screen. The
default current folder is the main folder and differs from any other user folder only
because it cannot be deleted. A temporary folder is created and named by the
system anytime a user function or program begins execution. Each new
function/program creates another temporary folder. When the function/program is
complete, the corresponding folder is deleted. The only variables in the
temporary folder are the parameters of the function/program and any variables
listed in a LOCAL command. System variables are considered to be outside the
folders (even though some, such as the graph functions, are actually in the main
symbol table). A specific user variable can be accessed from anywhere by
including the path (user folder and backslash) with the name. For example, folder
name\variable name. The following look-up paths are for the general case and
do not include all the flags, conditions, etc. that must be checked once the
variable has been found. See sections 13.3.2.2 Recall Look-up Path and
13.3.2.3 Store Look-up Path for details.
13.3.2.2.

Recall Look-up Path

Is the variable a system variable? These are special cases and cannot have
•
a specified path.
• If a complete path is specified, return the HSYM handle for that variable, or if
it does not exist, return H_NULL.
If there is a backslash followed by the variable name, return the HSYM
•
handle for that variable in the current user folder, or H_NULL if it does not
exist.
If there is not a path specified, check for that variable name in the current
•
temporary folder. If it exists, return the HSYM handle. There may be no data
associated with the variable yet if it was created by a LOCAL command but
has not been initialized.
If the variable does not exist in the current temporary folder, check the
•
current user folder. If it exists, return the HSYM handle.
Otherwise, the variable does not exist in the current path and H_NULL is
•
returned.
TI-89 / TI-92 Plus Developer Guide
Chapter 13: Memory Management
Not for Distribution Beta Version January 26, 2001