Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!ncar!midway!mimsy!mojo!russotto
From: russotto@eng.umd.edu (Matthew T. Russotto)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Variable length arrays in Pascal--can it be done?
Message-ID: <1991Apr3.034030.27719@eng.umd.edu>
Date: 3 Apr 91 03:40:30 GMT
References: <1521@babcock.cerc.wvu.wvnet.edu>
Sender: news@eng.umd.edu (C-News)
Organization: College of Engineering, Maryversity of Uniland, College Park
Lines: 31

In article <1521@babcock.cerc.wvu.wvnet.edu> un020070@vaxa.wvnet.edu writes:
>I want to have variable length arrays in Pascal.  Pascal, however,
>does not want me to have variable length arrays in it.  I think I've
>figured out a way to do this.  This solution is probably glaringly
>obvious to more experienced programmers, but I want to run it
>past you to see if there's any reason why it shouldn't work.
>
>Suppose I define a type in Pascal which is an arbitrarily large
>array: say, one with 10000 elements in it, or some number larger than
>I will ever need.  Suppose I then define a pointer to point to
>this type, and a handle to point to the pointer.  Let's say I want
>to start out with seven elements in the array, so I use NewHandle
>and allocate just enough memory to hold those seven elements.  I
>store this number seven in a variable to keep track of how big
>the array is.
>
>Now, as long as I am careful not to refer to any elements beyond the
>end of the memory block, I should not have any problems, right?
>And if I want to resize the array, I can use SetHandleSize,
>making sure to keep track of how many elements are now in the array,
>right?  Is there any reason why this shouldn't work?

I believe this is similiar to the way Apple does it for CTabHandles and other
variable-length arrays.  They declare theirs to be
TYPE
	CSpecArray: Array [0..0] of ColorSpec;
and turn off range checking so the references succeed.  If you want range
checking effective for other arrays, your method should work.
--
Matthew T. Russotto	russotto@eng.umd.edu	russotto@wam.umd.edu
     .sig under construction, like the rest of this campus.