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From: acm@Sun.COM (Andrew MacRae)
Newsgroups: comp.lang.pascal
Subject: Re: Overflow error
Message-ID: <4248@jethro.Corp.Sun.COM>
Date: 31 May 91 14:43:52 GMT
References: <675648024.0@nwark.FidoNet>
Sender: news@jethro.Corp.Sun.COM
Reply-To: acm@Sun.COM (Andrew MacRae)
Organization: Sun Microsystems, Mountain View CA
Lines: 96
Cc: acm

In article <675648024.0@nwark.FidoNet>, Alex.Brown@f1020.n391.z1.FidoNet.Org (Alex Brown) writes:
 > 
 >     I am getting an overflow error after 3 pages are displayed.  Can
 > any tell
 > why and how to avoid it in the future.
 
The problem is that you are calling the procedure getstring recursivly (that
is from within the procedure itself).  Rather than have that call to getstring
at the end of getstring, try using (yet another) WHILE loop testing for
eof outside the scope of the loop that is testing for eof and f < 25.

The reason I say 'yet another WHILE loop' is that you should learn how to
use the FOR loop.  Your code in the procedure showpage that sets f to 1, then
loops while incrementing f and testing for completion is in essence a FOR loop.

You are also going to run into problems of an interesting nature when displaying
the last page of a file, but I will let you discover how.  (It's a problem I
remember running into myself.)

						Andrew MacRae
						
 > 
 >    The program is supposed to grab 24 lines of a text and display them
 > with a
 >    >>>>>>>MORE<<<<<<<<  message at the bottom.
 > 
 > 
 > Program View;
 > uses dos, crt;
 > 
 > var
 >   ftext : text;
 >   f : integer;
 >   s : array[1..25] of string;
 > 
 > procedure showpage;
 >   begin
 >   f := 1;
 >   while f < 25 do
 >     begin
 >     writeln(s[f]);
 >     inc(f);
 >     end;
 >   end;
 > 
 > 
 > procedure getstring;
 >    begin
 >   f := 1;
 >   while (not eof(ftext)) and (f < 25) do
 >     begin
 >     readln(ftext, s[f]);
 >     inc(f);
 >     end;
 >   if not eof(ftext) then
 >     begin
 >     s[25] := '               >>>>>>>>MORE<<<<<<<< ';
 >     showpage;
 >     readln;
 >     end;
 >   getstring;
 >   end;
 
SUGGESTED:
		Procedure getstring;
		 Begin
		  While not EOF(ftext) do
		   Begin
		    f := 1;
		    While (not EOF(ftext)) and (f < 25) do
		     Begin
		      ReadLn(ftext, s[f]);
		      Inc(f)
		     End;
		    If not Eof(ftext) Then
		     Begin
		      s[25] := '               >>>>>>>>MORE<<<<<<<< ';
		      showpage;
		      ReadLn
		     End
		   End
		  End;
		  
 > 
 > begin
 >   if paramcount <> 1 then
 >     begin
 >       writeln('Syntax is  VIEW "filename" ');
 >       halt;
 >     end;
 >   assign(ftext,paramstr(1));
 > 
 >   reset(ftext);
 >   getstring;
 >   close(ftext);
 > end.