
(********************************************************************)
(*                                                                  *)
(*  logfile.s7i   Interface type describing log files.              *)
(*  Copyright (C) 1989 - 2018  Thomas Mertes                        *)
(*                                                                  *)
(*  This file is part of the Seed7 Runtime Library.                 *)
(*                                                                  *)
(*  The Seed7 Runtime Library is free software; you can             *)
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(*  Lesser General Public License as published by the Free Software *)
(*  Foundation; either version 2.1 of the License, or (at your      *)
(*  option) any later version.                                      *)
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(*  PURPOSE.  See the GNU Lesser General Public License for more    *)
(*  details.                                                        *)
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(*  Free Software Foundation, Inc., 51 Franklin Street,             *)
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(*                                                                  *)
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(**
 *  Interface type for log files.
 *  When [[string]] expressions are written to a ''logFile'' the
 *  evaluation of the string takes only place when the logFile is not
 *  STD_NULL. The logFile interface is implemented with [[null_file]],
 *  [[external_file]], [[utf8|utf8_file]], [[utf16|utf16_file]],
 *  [[socket]], [[echo|echo_file]], [[line|line_file]],
 *  [[dir|dir_file]] and many other types.
 *)
const type: logFile is sub file interface;


(**
 *  Write an evaluated [[string]] expression to a logFile.
 *  The evaluation of the string takes only place when the logFile
 *  is not STD_NULL.
 *)
const proc: write (inout logFile: log, ref func string: stri) is func
  local
    var file: aFile is STD_NULL;
  begin
    if log <> STD_NULL then
      aFile := log;
      write(aFile, stri);
    end if;
  end func;


(**
 *  Write an evaluated [[string]] expression followed by end-of-line to a logFile.
 *  The evaluation of the string takes only place when the logFile
 *  is not STD_NULL. The implementation function decides how writing
 *  end-of-line is done. It can be done by writing '\n', but other
 *  solutions are also possible.
 *)
const proc: writeln (inout logFile: log, ref func string: stri) is func
  local
    var file: aFile is STD_NULL;
  begin
    if log <> STD_NULL then
      aFile := log;
      writeln(aFile, stri);
    end if;
  end func;
