HP 39g Graphing Calculator - Manual (Page 230)

REPLACE
SUB
ZEROGROB
Replaces portion of graphic in graphicnamel with
graphicnamel, starting at position . REPLACE also works
for lists and matrices.
REPLACE graphicnamel; (position); graphicnamel:
Extracts a portion of the named graphic (or list or matrix), and
stores it in a new variable, name. The portion is specified by
position and positions.
SUB name; graphicname; (position); (positions):
Creates a blank graphic with given width and height, and
stores it in graphicname.
ZEROGROB graphicname; width; height:
Loop commands
DO...UNTIL
...END
WHILE...
REPEAT...
END
Loop structures allow a program to execute a routine
repeatedly. The HP 39G/40G has three loop structures. The
example programs below illustrate each of these structures
incrementing the variable A from 1 to 12.
Do ...Until... End isaloop structure that executes the/oop-
claiise repeatedly until test-clause returns a true (nonzero)
result. Because the test is executed after the loop-clause, the
loop-clause is always executed at least once. Its syntax is:
DO loop-clause UNTIL test-clause END
1 ► A:
DO A + 1 ► A
UNTIL A == 12
END
While ... Repeat... End is a loop structure that repeatedly
evaluates test-clause and executes loop-clause sequence if the
test is true. Because the test-clause is executed before the
loop-clause, the loop-clause is not executed if the test is
initially false. Its syntax is:
WHILE test-clause REPEAT loop-clause END
1 ► A:
WHILE A < 12
REPEAT A+1 ► A
END
15-22 Programming