The FOR 7 NEXT Structure

The syntax for this structure is

«… start finish FOR counter loop-clause NEXT … »

FOR … NEXT executes the loop-clause 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 loop-clause. The loop-clause is always executed at least once.

Syntax

Flowchart

 

Start

1:Start

 

finish

2:finish

 

FOR

counter=start

 

 

Store finish

 

loop-clause

Body of loop

 

 

counter = counter + 1

 

NEXT

 

 

 

Is

yes

 

counter ≤ finish?

 

 

 

no

 

FOR 7 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 loop-clause is executed — counter can appear within the loop-clause. NEXT increments counter by one, and then tests whether its value is less than or equal to finish. If so, the loop-clauseis repeated (with the new value of counter) — otherwise, execution resumes following NEXT. When the loop is exited, counter is purged.

To enter FOR 7 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 » »

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