LI-COR LI-6400, Руководство пользователя

Страница: 611 / 846

Programming with LPL
Pointers
Using the LI-6400 22-17
on the stack. Next comes a local pointer declaration leaving us with an object
named
whiteSpace
that points at the local array.
NOTE: If you change any values of a local array, or change the ready value,
those changes stay in effect
forever (or at least until the program is re-com-
piled). For example, consider Figure 22-6. The function
Test
is called two
times, and it contains a local CHAR array that gets modified each time
Test
is
called.
Figure 22-6 will produce the following when executed:
ABCD
BCD
Pointers
Pointers (type
PTR
) are a little more complicated that
INT
or
FLOAT
ob-
jects, but provide a lot of power and versatility to the LPL language. The Òval-
ueÓ of a pointer is the address and type of the object to which they point.
Pointers are initialized by reference to another object. Pointers can remain un-
initialized by substituting a 0 for the destination variable name.
We have seen pointers used already in Figure 22-6 on page 22-17. But point-
ers arenÕt restricted to being local objects. They can be declared out of func-
:FCT Main
{Test Test GETKEY }
Test
{
"ABCD" :PTR x
x "%s\n" PRINT
Add 1 to each element of the array, and set the size
to 3.
x 1 +
x 3 SETREADY
}
Figure 22-6. A local array phenomenon illustrated.