Texas Instruments TITANIUM TI-89 - Manual (Page 833)

Appendix A: Functions and Instructions 833
isLocked() CATALOG
isLocked(var_name)
⇒ ⇒ ⇒ ⇒ true,false
Determines if var_name is locked or not.
Returns true if var_name is locked or archived.
Returns false if var_name is not locked or
archived.
isLocked(PROG1) ¸ False
isPrime() MATH/Test menu
isPrime( number )
⇒ ⇒ ⇒ ⇒ Boolean constant expression
Returns true or false to indicate if number is a
whole number ‚ 2 that is evenly divisible only by
itself and 1.
If number exceeds about 306 digits and has no
factors  1021, isPrime( number ) displays an
error message.
If you merely want to determine if number is
prime, use isPrime() instead of factor() . It is
much faster, particularly if number is not prime
and has a second-largest factor that exceeds
about five digits.
IsPrime(5) ¸ true
IsPrime(6) ¸ false
Function to find the next prime after a specified
number:
Define nextPrim(n)=Func:Loop:
n+1!n:if isPrime(n):return n:
EndLoop:EndFunc ¸ Done
nextPrim(7) ¸ 11
isVar()
CATALOG
isVar(var_name) ⇒ ⇒ ⇒ ⇒ true,false
Determines if var_name is in use. Returns true
if var_name exists. Returns false if var_name
does not exist.
isArchiv(PROG1) ¸ True
Item CATALOG
Item itemNameString
Item itemNameString , label
Valid only within a Custom...EndCustm or
ToolBar...EndTBar block. Sets up a drop-down
menu element to let you paste text to the cursor
position (
Custom ) or branch to a label
( ToolBar ).
Note: Branching to a label is not allowed within
a
Custom block.
See Custom example.
Lbl CATALOG
Lbl labelName
Defines a label with the name labelName in the
program.
You can use a Goto labelName instruction to
transfer program control to the instruction
immediately following the label.
labelName must meet the same naming
requirements as a variable name.
Program segment:
©
:Lbl lbl1
:InputStr "Enter password", str1
:If str1ƒpassword
: Goto lbl1
:Disp "Welcome to ..."
©