Texas Instruments TI-89 User Manual - Page 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) ¸ IsPrime(6) ¸ true 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 isArchiv(PROG1) ¸ True Determines if var_name is in use. Returns true if var_name exists. Returns false if var_name does not exist. 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 ..." © Appendix A: Functions and Instructions 833