Pointers to String Arrays

[Joe Speroni]

I need (strong want) to access a group or unrelated string arrays
by an index number.

Apparently it is possible to get and save the ptr to an entire
array, e.g.
DIM R(1:4) as string
DIM xptr AS STRING PTR
xptr=VARPTR(R())

but having saved it, what is the syntax to access the elements
of the array,

I've tried several ways. Here's two (commented out lines) that
don't work.
----------------------------------------------------------------
$COMPILE EXE
FUNCTION PrintX(A() AS STRING) AS STRING
FOR i&=1 TO 4:x$=x$+A(i&)+"|":NEXT:MSGBOX x$
END FUNCTION

FUNCTION PBMAIN() AS LONG
DIM R(1:4) AS STRING
R(1)=" String I. ":R(2)=" String II. "
R(3)=" String III. ":R(4)=" String IV. "

DIM xptr AS STRING PTR
xptr=VARPTR(R())

MSGBOX PrintX(R())
'MSGBOX PrintX(xptr) ' This won't work
'FOR i&=1 TO 4:[email protected](i&)+"|":NEXT:msgbox x$ ' Nor does this

MSGBOX "end program"
END FUNCTION

[Michael Mattias]

You're doing this the hard way.

Just call your function, pass it the array...

MyFunc$ = PrintX(R())

FUNCTION PrintX (A() AS STRING ) AS STRING
... whatever

END FUNCTION

No need to mess with pointers here.
MCM

[Joe Speroni]

Michael, I'll grant you that if the idea was to code the example program
I used, you are correct. But I'm looking at how to set up an array of
pointers so that that I can access the array from a CALLBACK function
using an index calculated from the CBCTL value. Inside the CALLBACK
function all I have is a single number. I want to get to the array via
its pointer.

[Michael Mattias]

Well, why didn't say what you wanted?

I asked about this a couple of weeks ago, and the answer was there is not in the current PB compilers any mechanism to access arrays given only the address of(pointer to)the array descriptor, but this is 'on the list' of features for consideration.

What you want to do is not save a pointer to the array descriptor, but a pointer to the first element of the string array using VARPTR (not STRPTR) and use index pointers to get at the various elements. Treat the array elements as STRING PTRs and this should work (I did not test this).




-------------
Michael Mattias
Racine WI USA
[email protected]