Checkcurrent - Texas Instruments TI-89 Developer's Manual

Appendix A: System Routines — Variables

checkCurrent

Declaration: HSYM checkCurrent (EStackIndex symName , BYTE tag )
Category(ies): Variables, Data Utilities
Description: Make sure the given symbol exists and matches the requested tag type.
Inputs: symName — Indexes the symbol name to check (points to the zero byte
tag
Outputs: HSYM of the symbol table entry if it exists and matches the requested tag
type, otherwise returns H_NULL.
Assumptions: None
Side Effects: None
Availability: All versions of the TI-89 / TI-92 Plus.
TI-89 / TI-92 Plus
Differences: None
See Also: VarRecall, TokenizeSymName
Example: The text editor when it is told to edit the current text variable uses
checkCurrent to make sure the previous name entered by the user still
exists and is a text variable. If it is not then it falls through to the code to
prompt the user for a new text variable to edit.
static EStackIndex curTextNameSym;
HSYM hSym;
.
.
.
case AP_START_CURRENT:
// Does current text exist?
hSym = checkCurrent(curTextNameSym, TEXT_VAR_TAG);
if (hSym != H_NULL)
break;
// Fall through to open new text
case AP_START_NEW:
// Prompt for new text name
hSym = VarNew((BYTE *)types);
TI-89 / TI-92 Plus Developer Guide
terminator).
— Requested tag type.
/* text exist? */
/* yes, open existing text ---> */
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Beta Version January 26, 2001