HP 50g Graphing manual For Next Structure, « … start finish for counter loopclause Next … »

The FOR NEXT Structure

The syntax for this structure is

«… start finish FOR counter loopclause NEXT … »

FOR … NEXT executes the loopclause program segment one time for each number in the range start to finish, using local variable counter as the loop counter. You can use this variable in the loopclause. The lo opclause is always executed at least once.

Syntax

Start

finish

FOR

loop-clause

NEXT

Flowchart

1:Start

2:finish

counter=start Store finish

Body of loop

counter = counter + 1

Isyes

counter ≤ finish?

no

FOR NEXT Structure

FOR takes start and finish from the stack as the beginning and ending values for the loop counter, then creates the local variable counter as a loop counter. Then the loopclause is execute d — counter can appear within the loopclause. NEXT increments counter by one, and then tests whether its value is less than or equal to finish. If so, the loopclause is repeated (with the new value of counter) — otherwise, execution resumes following NEXT. When the loop is exited, counter is purged.

To enter FOR NEXT in a program:

Press !°%BRCH% ! %FOR%.

Example: The following program places the squares of the integers 1 through 5 on the stack:

«1 5 FOR j j SQ NEXT »

Example: The following program takes the value x from the stack and computes the integer powers i of x. For example, when x =12 and start and finish are 3 and 5 respectively, the program returns 123, 124 and 125. It requires as inputs start and finish in level 3 and 2, and x in level 1. (→ x removes x from the stack, leaving start and finish there as arguments for FOR.)

«→ x « FOR n 'x^n' EVAL NEXT » »

120 RPL Programming