files with pointers/linklists

easler

Hey guys!

How do I read in a file using pointers? I'm just beginning to program and I am a little confused on this.

Thanks.

zibadian

: Hey guys!
:
: How do I read in a file using pointers? I'm just beginning to program and I am a little confused on this.
:
: Thanks.
:
This involves two steps:
1st you need to create the poiner using GetMem() or New().
2nd you need to read the value into the dereference pointer.

Example:
[code]
type
MyIntPtr = ^integer;
var
i: MyIntPtr;
f: text;
begin
MyIntPtr := New(MyIntPtr);
Assign(f, 'somefile.dat');
Reset(f);
read(f, i^); { dereferenced pointer }
close(f);
end;
[/code]
A linked list is similar, but a little more involved:
[code]
type
PIntegerItem = ^TIntegerItem;
TIntegerItem: record
Value: integer;
Next: PIntegerItem;
end;
var
List, Current: PIntegerItem;
f: text;
begin
Current := nil; { Make sure current is nil }
Assign(f, 'somefile.dat');
Reset(f);
while not eof(f) do begin
if Current = nil then begin { Reading first value }
Current := New(PIntegerItem);
List := Current;
end else begin { Reading second and further values }
Current^.Next := New(PIntegerItem);
Current := Current^.Next;
end;
read(f, Current^.Value); { Actual reading }
end;
close(f);
end;
[/code]
I highly recommend that you do NOT save and read the actual pointer values, because these might be different each time the program runs.