1-22 RPL Programming
! «!!…!DO!loop-clause!UNTIL!test-clause!END!…!»
DO… UNTIL… END executes the loop-clause sequence repeatedly until test-clause returns a true (nonzero)
result. Because the test-clause is executed after the loop-clause, the loop-clause is always executed at least once.
Syntax Flowchart
UNTIL
END
Body of loop
TEST
Is test
result non-zero?
no
yes
1: test result
test-clause
DO
loop-clause
DO … UNTIL … END Structure
DO starts execution of the loop-clause. UNTIL marks the end of the loop-clause. The test-clause leaves a test
result on the stack. END removes the test result from the stack. If its value is zero, the loop-clause is executed
again — otherwise, execution resumes following END. If the argument of END is an algebraic or a name, it's
automatically evaluated to a number.
To enter DO … UNTIL … END in a program:
! Press !°%BRCH% ! %DO%.
Example: The following program calculates n + 2n +3n + … for a value of n. The program stops when the
sum exceeds 1000, and returns the sum and the coefficient of n.
Program: Comments:
"!
452!3!
#!G!Z!&
Duplicates n, stores the value into
n and s, and initializes c to 1.
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