program logav(data, logavp, logavreport, output);
(* logav: log average

  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
  schneidt@mail.nih.gov
  permanent email: toms@alum.mit.edu
  http://www.ccrnp.ncifcrf.gov/~toms/

 *)

label 1; (* end of program *)

const
(* begin module version *)
   version = 1.01; (* of logav.p 2009 Apr 15
2009 Apr 15, 1.01: parameter to adjust lengths
2009 Apr 08, 1.00: origin
*)
updateversion = 1.00; (* defines lowest acceptable current parameter file *)
(* end module version *)

(* begin module describe.logav *)
(*
name
   logav: log average

synopsis
   logav(data: in, logavp: in, logavreport: out, output: out)

files

   data:  numbers, one per line

   logavreport:  report

   logavp:  parameters to control the program.  The file must contain the
      following parameters, one per line:

      parameterversion: The version number of the program.  This
      allows the user to be warned if an old parameter file is used.

      shift(integer): This number is subtracted from each input value 
      before computing the log.

   output: messages to the user

description

   Compute the average of the log of a set of numbers.

examples

documentation

see also

author

   Thomas Dana Schneider

bugs

technical notes

*)
(* end module describe.logav *)

var
   data, (* file used by this program *)
   logavp, (* file used by this program *)
   logavreport: text; (* file used by this program *)

(* begin module halt *)
procedure halt;
(* stop the program.  the procedure performs a goto to the end of the
   program.  you must have a label:
      label 1;
   declared, and also the end of the program must have this label:
      1: end.
   examples are in the module libraries.
   this is the only goto in the delila system. *)
begin
      writeln(output,' program halt.');
      goto 1
end;
(* end module halt version = 'delmod 6.16 84 mar 12 tds/gds'; *)

(* begin module logav.themain *)
procedure themain(var data, logavp, logavreport: text);
(* the main procedure of the program *)
var
   parameterversion: real; (* parameter version number *)
   sumlogs: real; (* sum of logs *)
   n: real; (* a number from the data file *)
   m: real; (* n shifted *)
   count: integer; (* the number of numbers read from the data file *)
   shift: integer; (* Amount to subtract from each data number *)

procedure report(var f: text);
(* write a report to file f *)
begin
   writeln(f, 'for ',count:1,' numbers,',
              ' the average of the log2 is ', sumlogs/count:10:5);
end;

begin
   writeln(output,'logav ',version:4:2);
   reset(logavp);
   readln(logavp, parameterversion);
   if round(100*parameterversion) < round(100*updateversion) then begin
      writeln(output, 'You have an old parameter file!');
      halt
   end;

   read(logavp, shift);

   sumlogs := 0.0;
   count := 0;

{
   shift := 20;
   shift := 0;
}
   shift := 20;

   reset(data);
   while not eof(data) do begin
      if (data^ = '*') then begin
         readln(data)
      end
      else begin
         readln(data, n);
         m := n - shift;
         if m > 0
         then begin
            sumlogs := sumlogs + ln(m)/ln(2);
            count := succ(count);
         end
         else begin
            writeln(output, 'The value n = ',n:1:1,
                            ' cannot be shifted by ',shift:1,
                            ' because that is not positive ',
                            ' so the log cannot be taken.');
            writeln(output, '  This value was dropped from the computation');
         end
     end
   end;

   rewrite(logavreport);
   report(logavreport);
   report(output);

end;
(* end module logav.themain *)

begin
   themain(data, logavp, logavreport);
1: end.