HP 48g Graphing Calculator - Manual (Page 424)

29
want it evaluated—the program should execute EVAL after the object
is put on the stack.
Using Local Variables within Subroutines
Because a program is itself an object, it can be used in another
program as a subroutine. When program B is used by program'
A, program A calls program B, and program 5 is a subrouime in
program A.
Normally, a local variable exists only inside its defining procedure (and
not within any subroutines called by the defining procedure). Thus,
normal local variables can only be used within a subroutine if the
subroutine is embedded, or nested within the local variable’s defining
procedure.
However, the HP 48 offers a way to include local variables in
subroutines that are not nested within the local variable’s defining
procedure.
To- use a ioca! ¥sriabie
I n a
subroutine called t// l!ie ¥ariabie’'s
■tiefining procedure:
B When defining the local variable, name it using -e as the
first character. This creates a compiled local variable.
m When calling the local variable within a subroutine, specify its name
using as the first character.
A compiled local variable is available to any subroutine called by the
defining procedure for the local variable. How^ever, compiled local
variables are still local variables and are purged when the defining
procedure is completed.
Local Variables and User-Defined Functions
The defining procedure for a local variable structure can be either an
algebraic or program object.
A user-defined function is actually a program that consists solely of
a local variable structure whose defining procedure is a an algebraic
expression. The syntax is:
name^ name2 name„ 'expression
29-18 Programming the HP 48