Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!sdd.hp.com!ucsd!ucbvax!LSUVM.BITNET!$CSF214
From: $CSF214@LSUVM.BITNET (John Mills)
Newsgroups: comp.sys.apple2
Subject: Re: new() procedure in Pascal
Message-ID: <9009141703.AA15123@apple.com>
Date: 14 Sep 90 15:37:47 GMT
References: <vax5!q4kx@CU-ARPA.CS.CORNELL.EDU>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 38

Joel Sumner <vax5!q4kx@CU-ARPA.CS.CORNELL.EDU> writes:

>One more Pascal related question.  When should I call the following?
>
>var   p:pointer (or StringPtr, or anything pointer)
>begin
>....
>new(p);
>....
>end;
>
>In other words, when do you have to call new()?  Only when it is defined
>in 'var' headings?  Only global 'var' headings?  How about as value parameters
>of a procedure/function?  I was writing a program that kept crashing
>(corrputed string) until I called new(mystringptr).  But I have made
>other programs before that do similar things and I never used new().  I
>am confused.  Someone please help me.
>
>Thanks

  Joel, you have defined the variable "p" to be of type "pointer" in this
example. A pointer can be thought of as a variable holding an integer
number, which is in itself the address, in memory, of some data structure
(be it integer, record, whatever).
  When you test-run the program, NEVER assume that your variables have some
pre-initialized value; i.e. all variables are assumed to be UNDEFINED
in value. This is what the "new(p)" procedure is for. Specifically, the
"new" procedure allocates storage space in memory for the "pointed-to"
data structure and then puts the address of the storage space in the
variable "p".
  In short, to answer your question "when do you have to call new()," I
would say use it whenever you need to create new storage space for
your data structure.

========================================
 Bitnet : $csf214@lsuvm
 Internet : $csf214@lsuvm.sncc.lsu.edu
========================================