Texas Instruments TI-89 Developer's Manual page 182

140
For example:
HSYM hsym;
SYM_ENTRY *symp;
EStackIndex estackIndex, nPtr;
hsym = VarRecall( nPtr, 0 );
if( hsym ) {
symp = DerefSym( hsym ) ;
if( symp->hVal ) {
estackIndex = HToESI( symp->hVal );
/* estackIndex points to the last byte of the data,
*/
.
.
.
VarRecall may throw the following errors:
INVALID_PATHNAME_ERROR
ER_FOLDER
ER_INVALID_VAR_REF
ER_RESERVED
ER_UNDEFINED_VAR
Most system variables cannot be used in a function that is being graphed, either
because they change too often or because they are used by the graph routines
themselves (for example, xmin or xc). When these variables are accessed while
graphing, an error is reported by VarRecall. Locked variables may be looked up
with VarRecall.
TI-89 / TI-92 Plus Developer Guide
/* hVal is the handle to the data part of the
variable which can also be null. */
which contains the type tag.
Not for Distribution
Chapter 13: Memory Management
/* handle */
/* pointer */
/* pointer */
/* where nPtr is the pointer to the
variable name in tokenized format */
/* symp points to symbol table entry */
— Invalid variable name.
— The variable is a folder.
— The variable cannot be referenced in the
current mode. Some variables are only
accessible by the application that created
them, like C1 . . . C99, which can only be
accessed by the data matrix editor. Other
variables can only be accessed under certain
conditions, like the stat variables, which can
only be accessed if a stat calculation has been
made.
— The VR_NO_SYS_VARS flag was set and the
variable to be recalled was a system variable.
— Normally, H_NULL is returned if the variable is
not found. This error is thrown if an attempt is
made to execute an undefined function while
graphing.
Beta Version January 26, 2001