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Author: Mats Ohlin, FOA 1, S-104 50 STOCKHOLM 80, SWEDEN.
Version 1.0
Date: 76-01-16

The DAHELP class may be used in order to save core in
application programs when the HELP texts are very long
and/or many.

If you prepare a number of sequential files with names equal to
the respective keywords, the MAKHLP program may be used in order
to create a DAHELP direct access file. This file could then
be used by the DAHELP class in order to display any of the included
(sub)files on the TTY (Sysout i.e.). It is also possible to
make DAHELP list all entries (keywords) in the DAHELP file.

Calling the boolean procedure HELPLIST("abc") will search for
the first entry STARTING with "ABC" (starting at col. 10!)
in the directfile specified by the single parameter to DAHELP
(default extension is .HLP). If the file is not found,
HELPLIST will return FALSE.

HELPLIST("?") will produces a listing of available entries preceded
by the text in the DAHELP text attribute DIRLINE.

The text will be displayed SCREENLINES lines at a time
(default value = 20). If SCREENLINES is set to zero the full text
will be displayed without interrupt. At interrupt, a prompting
message - the DAHELP text attribute PROMPTLINE is displayed
and the user may either continue the output by pressing
the RETURN key, or skipping output by pressing the ESCAPE key (ALTMODE).
Any other answer will give a help message.

Example of use:

  EXTERNAL REF (Directfile) PROCEDURE finddirectfile;
  REF (dahelp) dah;

      dah:- NEW dahelp("X");	! Uses file "X.HLP" ;
      dah.helplist("Enter a");	! Gives info on lines 2-3 in
 				! example below;
 				! The texts will be Uppercased
 				! before comparison.
      dah.helplist("?");	! Gives typeout of entries;
      dah.stop;			! Closes the help file;
 				! If the attribute AUTOCLOSE
 				! is set to TRUE, then
 				! the file will be closed
 				! after every procedure call.
 				! DAHELP will thus run more
 				! efficiently if you use
 				! the STOP procedure when you
 				! are ready instead.;


Calling HELPLIST will have the side-effect of setting
Sysout.linecount := -1;  (no form feeds).

The DIRED program may be used to modify the file.
Again - the Imagesize of the directfile must be 73!

The text in the HELP directfile (imagelength 73) should
conform to the following format (which is obeyed automatically
if you use MAKHLP):

Col.1    Col.10
 |        |
 ~M       Enter a
 ... help text for
 ... question starting with "Enter a
 ~N       Enter b
 ... help text for
 ... question starting with "Enter b

The contents of each subsection should be:

A. The first RECORD should contain:

   1. ~ (tilde - ASCII 176 octal) in column 1

   2. The Number Field - refering to start of next section.
      The record number for the start of the next subsection
      (in the example above M is 5) - if none then -1 (N),
      should be placed in the field col.2 to 9.

   3. The Entry Field - containg to Search Key.
      This UPCASED text should start at pos. 10.

B. The HELP text

C. ~0 in col.1 and 2

The Number Field for the last subsection should be -1.

It is possible to add additional text to a subsection by
ending it with ~xxx (instead of ~0) where xxx is the record
number where the text continues.

It is thus possible to have common final parts of several
subsections. NOTE! It is possible to create eternal loops if
you jump backwards in the file - so beware of such loops!

The following example shows the outline of a more general
Helping Program:

    TEXT file;
    EXTERNAL TEXT PROCEDURE conc,rest,upcase,checkextension;
    EXTERNAL INTEGER PROCEDURE checkint,scanint;
    EXTERNAL REF (Directfile) PROCEDURE finddirectfile;
    EXTERNAL CLASS dahelp;

    Outtext("File:"); Breakoutimage;
    IF Lastitem THEN GO TO quit;
    file:- Intext(Sysin.Length-Sysin.Pos+1).Strip;
    IF upcase(file) = "EXIT" THEN GO TO quit;

    dahelp(file) BEGIN
	TEXT q;
	Outtext("DIR::"); Outimage;
	! Listing available entries;
	IF NOT helplist("?") THEN GO TO start;
	nexthelp:   dotypeout(Sysout);
	Outtext("*"); Breakoutimage;
	IF Lastitem THEN GO TO exit;
	q:- Intext(Sysin.Length-Sysin.Pos+1).Strip;
	IF upcase(q) = "EXIT" THEN GO TO exit;
	IF q = "END" THEN BEGIN  stop;    GO TO start   END;
	GO TO IF NOT helplist(q) THEN start ELSE nexthelp;
	exit: stop;

Use of DAHELP together with SAFEI(O) and SAFMIN:

If you use the call HELPLIST(MAINPROMPT) as actual 5th parameter
to REQUEST procedures, the actual prompting question will be used
as search key in the DAHELP file. Note that DAHELP will use the
FIRST entry where the beginning of the Entry Field equals the
Helplist parameter.

		[End of DAHELP.HLP]