Reference Guide

RPL Programming 1-25
Using Loop Counters
For certain problems you may need a counter inside a loop structure to keep track of the number of loops. (This
counter isn’t related to the counter variable in a FOR … NEXT/STEP structure.) You can use any global or local
variable as a counter. You can use the INCR or DECR command to increment or decrement the counter value and
put its new value on the stack.
The syntax for INCR and DECR is
« … ' variable ' INCR … »
or
« … ' variable ' DECR … »
To enter INCR or DECR in a program:
 Press !° #MEM# %ARITH% %INCR% or %DECR% .
The INCR and DECR commands take a global or local variable name (with ' delimiters) as their argument — the
variable must contain a real number. The command does the following:
1. Changes the value stored in the variable by +1 or -1.
2. Returns the new value to the stack.
Example: If c contains the value 5, then 'c' INCR stores 6 in c and returns 6 to the stack.
Example: The following program takes a maximum of five vectors from the stack and adds them to the current
statistics matrix.
Program: Comments:
«
0 → c
Stores 0 in local variable c.
«
Starts the defining procedure.
WHILE
Starts the test clause.
DUP TYPE 3 ==
Returns true if level 1 contains a vector.
'c' INCR
Increments and returns the value in c.
5 ‰
Returns true if the counter c≤5.
AND
Returns true if the two previous test
results are true.
REPEAT
Σ+
Adds the vector to ΣDAT.
END
Ends the structure.
»
Ends the defining procedure.
»