Islocked(), Isprime(), Isvar() – Texas Instruments TITANIUM TI-89 User Manual
Page 833: Item, Appendix a: functions and instructions 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 ..."
©