Example: Multiple Conditional Actions. The following program stores the level 1 argument in a variable if the argument is a string, list, or program.
Program: | Comments: |
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→ y | Defines local variable y. |
« | Starts the defining procedure. |
CASE | Starts the case structure. |
y TYPE 2 SAME | Case 1: If the argument is a string, stores |
THEN y 'STR' STO END | it in STR. |
y TYPE 5 SAME | Case 2: If the argument is a list, stores it |
THEN y 'LIST' STO END | in LIST. |
y TYPE 8 SAME | Case 3: If the argument is a program, |
THEN y 'PROG' STO END | stores it in PROG. |
END | Ends the case structure. |
» | Ends the defining procedure. |
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Using Loop Structures
You can use loop structures to execute a part of a program repeatedly. To specify in advance how many times to repeat the loop, use a definite loop. To use a test to determine whether or not to repeat the loop, use an indefinite loop.
Loop structures let a program execute a sequence of commands several times. Loop structures are built with commands — called structure words — that work only when used in proper combination with each other. These
loop structure commands are contained in the PRG BRCH menu (!°%BRCH%):
START … NEXT and START … STEP.
FOR … NEXT and FOR … STEP
DO … UNTIL … END.
WHILE … REPEAT … END.
In addition, the Σ function provides an alternative to definite loop structures for summations.
Using Definite Loop Structures
Each of the two definite loop structures has two variations:
NEXT. The counter increases by 1 for each loop.
STEP. The counter increases or decreases by a specified amount for each loop.
RPL Programming