The While Construct - HP 50g User Manual

Graphing calculator.

The WHILE construct

The general structure of this command is:
WHILE logical_statement REPEAT program_statements END
The WHILE statement will repeat the program_statements while
logical_statement is true (non zero). If not, program control is passed to
the statement right after END. The program_statements must include a
loop index that gets modified before the logical_statement is checked at
the beginning of the next repetition. Unlike the DO command, if the first
evaluation of logical_statement is false, the loop is never executed.
Example 1 – calculate the summation S using a WHILE...REPEAT...END
construct
The following program calculates the summation
Using a WHILE...REPEAT...END loop:
«
«
0.
n S
END S "S"
TAG " "
Store this program in a variable @@S4@@. Verify the following exercises: J
3 @@@S4@@
Result: S:14
5 @@@S4@@
Result: S:55
10 @@@S4@@
Result: S:385
30 @@@S4@@
Result: S:9455
Example 2 – generate a list using a WHILE...REPEAT...END construct
Type in the following program
«
xs xe dx
'x<xe' REPEAT 'x+dx' EVAL DUP 'x' STO END n
WHILE 'n 0' REPEAT n SQ S + 'S' STO n 1 – 'n' STO
«
xe xs – dx / ABS 1. + xs
n
2
S
k
k
0
4 @@@S4@@
8 @@@S4@@
20 @@@S4@@
100 @@@S4@@
Result: S:30
Result: S:204
Result: S:2870
Result: S:338350
«
n x
xs WHILE
LIST " " "
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