HP 50G, User Manual

Page: 710 / 887

Page 21-63
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 « WHILE
‘
n
≥
0
‘
REPEAT n SQ S +
‘
S
‘
STO n 1 –
‘
n
‘
STO
END S
“
S
” →
TAG
» »
Store this program in a variable
@@S4@@
. Verify the following exercises:
J
3
@@@S4@@
Result:
S:14
4
@@@S4@@
Result:
S:30
5
@@@S4@@
Result:
S:55
8
@@@S4@@
Result:
S:204
10
@@@S4@@
Result:
S:385
20
@@@S4@@
Result:
S:2870
30
@@@S4@@
Result:
S:9455
100
@@@S4@@
Result:
S:338350
Example 2 – generate a list using a WHILE…REPEAT…END construct
Type in the following program
«
→
xs xe dx « xe xs – dx / ABS 1. + xs
→
n x « xs WHILE
‘
x<xe
‘
REPEAT
‘
x+dx
‘
EVAL DUP
‘
x
‘
STO END n
→
LIST
» » »
∑
=
=
n
k
k S
0
2