program diffint(input,output);
(* differences between integers.

  Dr. Thomas D. Schneider
  National Institutes of Health
  National Cancer Institute
  Center for Cancer Research Nanobiology Program
  Molecular Information Theory Group
  Frederick, Maryland  21702-1201
  toms@ncifcrf.gov
  permanent email: toms@alum.mit.edu
  http://www.ccrnp.ncifcrf.gov/~toms/

*)

const
(* begin module version *)
   version = 1.07; (* of diffint.p 2007 Nov 29
2007 Nov 29, 1.07: rename difint as diffint
2007 Nov 28, 1.06: rename difint as diffint
1996 Oct 24, 1.05: functional
1986 dec  2, 1.00: origin
*)
(* end module version *)

(* begin module describe.diffint *)
(*
name
   diffint: differences between integers

synopsis
   diffint(input: in, output: out);

files
   input: a set of integers, one per line.
       Lines that begin with "*" are ignored.

   output: the difference between each integer and the previous one.

describe

   Lines that begin with an asterisk ('*') are first copied to the
   output.  then the difference between each integer in input and the
   previous one is given to the output.

documentation

see also

   {Program that allows selection of columns and ranges of differences
    to be selected:} diffintcut.p

author

   Thomas Dana Schneider

bugs

technical notes

   The program originally acted as if the integer before the first one
   is zero, but this creates artifacts.  The initial data point is now
   dropped.  However, data often comes separate into chunks.  This is
   marked by the comments.  So the program resets everytime there is a
   comment line.

   The name was changed to diffint (from difint) because that's
   closer to the Unix diff command.

bugs
   none known

*)
(* end module describe.diffint *)

var
   current, previous: integer; (* two integers from the input file *)
   haveprevious: boolean; (* do we have the previous value? *)

begin

   haveprevious := false;
   while not eof(input) do begin
      if input^='*' then begin
         (* copy lines beginning with '*' to output *)
         while not eoln(input) do begin
            write(output,input^);
            get(input);
         end;
         haveprevious := false;
         readln(input);
         writeln(output)
      end
      else begin
         readln(input, current);
         if haveprevious then writeln(output,current-previous:10);
         haveprevious := true;
         previous := current;
      end;
   end
end.