HP 48GII - Page 41

RPL Programming 1-15
To enter CASE … END in a program:
1. Press !°%BRCH% !%CASE% to enter CASE … THEN …END…END
2. For each additional test-clause, move the cursor after a test-clause END and press @%CASE% to enter THEN
… END.
Conditional Examples
These examples illustrate conditional structures in programs.
Example: One Conditional Action. The programs below test the value in level 1 — if the value is
positive, it's made negative. The first program uses a command sequence as the test-clause:
! "!452!67!8!9!:;<=!=<>!<=4!1!
The value on the stack must be duplicated because the > command removes two arguments from the stack (0.
and the copy of the value made by DUP).
The following version uses an algebraic as the test clause:
! "!#!?!"!?!67!+?98+!:;<=!=<>!<=4!1!1!
The following version uses the IFT command:
! "!452!8!9!"!=<>!1!67:!1!
Example: One Conditional Action. This program multiplies two numbers if both are nonzero.
Program: Comments:
"!
!#!?!@!
Creates local variables x and y containing
the two numbers from the stack.
!"!
!!67!
!!!+?A8+!
!
!!!+@A8+!
!
!!!B=4!
!
!!!:;<=!
!
!!!?!@!.!
!
Starts the test-clause.
Tests one of the numbers and leaves a test
result on the stack. Tests the other
number, leaving another test result on the
stack. Tests whether both tests were true.
Ends the test-clause, starts the true-
clause.
Multiplies the two numbers together only
if AND returns true.
!!!<=4!
!!1!
1!
Ends the true-clause.
The following program accomplishes the same task as the previous program:
! "!#!?!@!"!67!+?!B=4!@+!:;<=!?!@!.!<=4!1!1!
The test-clause 'x AND y' returns “true” if both numbers are nonzero.
The following version uses the IFT command:
! "!#!?!@!"!!+?!B=4!@+!+?.@+67:!1!1!
Example: Two Conditional Actions. This program takes a value x from the stack and calculates (sin x) /x.
At x= 0 the division would error, so the program returns the limit value 1 in this case.
! "!#!?!"!67!+?C8+!:;<=!?!D6=!?!,!<ED<!3!<=4!1!1!
The following version uses IFTE algebraic syntax: