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SAFEIO is a SIMULA external class which can be used when
writing the conversational parts of SIMULA programs.

The SAFEIO system offers the following facilities in
a single procedure call :

1.	Issue a prompting question to the user.

2.	Store the input in a simple variable.

3.	Optionally accept default answers (equal to CR).

4.	Check the syntax of the input.

5.	Issue an appropriate message if the input is invalid.

6.	Issue a informative message if the user responds with
	anything starting with a questionmark '?'.

7.	Allow the user to substitute tty input for disk file input.
	This may be requested at any question.

8.	Allow the user to save all accepted program input on a disk file.
	This file may be used as an input file in a subsequent run.
	Correspondence between saved and current question will
	be checked (option by default).

It is assumed that the user types in only one item into each
input line.

The format of a question to the user is:

REQUEST("prompting question",default,***input(variable,validity),
" error message if not valid",helpproc_expression);

The parameter default is a text variable or text constant
(or may be a call of a text procedure). There is a SAFEIO attribute
NODEFAULT which can be used if default answers should be

For the BOOLINPUT procedure there is only one argument though, the
receiving variable.

The validity is usually a boolean expression involving the
variable but may also be a call of a boolean procedure
if more complicated validity checking is necessary.
If the SAFFEIO attribute CHECKVALIDITY is set to FALSE, no
validity checking (i.e. no evaluation of the 2nd parameter to
the ***input procedure) will occur, thus speeding up
SAFEIO execution. Note, however that this will endanger the
security of your program.

The error message is printed if the validity becomes FALSE.
The prompting question will then be repeated.

The helpproc_expression which will be evaluated each time the
user types in an answer beginning with a questionmark '?'.

The SAFEIO boolean procedure HELP (with one text parameter =
the help text) may be used for displaying a text on the user's TTY.

If no special information should be issued the SAFEIO procedure
NOHELP may be used. (The message - "There is no help in this case."
will be issued.)

Some examples:

    EXTERNAL REF (Infile) PROCEDURE findinfile;
    EXTERNAL REF (Outfile) PROCEDURE findoutfile;
    EXTERNAL TEXT PROCEDURE conc,upcase,frontstrip,rest,checkextension;
    EXTERNAL CHARACTER PROCEDURE fetchar,findtrigger;
    EXTERNAL INTEGER PROCEDURE checkreal,checkint,scanint,ilog;
    EXTERNAL CLASS safeio;

    safeio(..<name of recording file saving the input or "">,
	<"English" or "Swedish">..)
	! Use "English" if english texts are wanted.
	  Use "Swedish" if swedish texts are wanted. ;

	TEXT ARRAY table[1:4];

	request("Enter integer:","14",intinput(i,irange(i,1,20)),
	   outofirange(1,20),help(" issued at '?'.."));

	! The default value is 14. Only positive numbers are allowed.;
	! Note the use of the procedures IRANGE(i,low,high) and
	! OUTOFIRANGE(i,low,high). See also Summary Chapter 5
	! in SAFEIO.MAN.;

	request("Enter real item:",nodefault,realinput(x,TRUE),"",nohelp);

	! Default answer not allowed. Any legal real item is accepted
	  since validity is TRUE. No help information available.;

	request("Enter long real value:","E1",longrealinput(y,y NE 0),
	   "? Must not be zero.",nohelp);

	! Default value is 10 = E1;

	request("Enter yes or no:",nodefault,boolinput(b),"",nohelp);

	! Note that procedure boolinput has just one parameter.;

	table[1]:- Copy("START");
	table[2]:- Copy("END");
	table[3]:- Copy("GO");
	table[4]:- Copy("GOTO");

	request("Enter command:",nodefault,textinput(t,menu(t,i,table,4)),

	! Note that the table must contain no lower case letters.
	  The user may use an abbreviated form when no ambiguity exists.
	  (Exact matches are always considered correct.)
	  The variable i will return the table index.
	  The length of the table (4) must also be supplied.
	  Note that the table must contain upper case letters only.
	  The procedure MENU resides in LIBSIM and checks
	  for correspondence between the T and the table.
	  The text procedure commandmessage will tell the user
	  if his (illegal) command was either Unknown or Ambigious.;

	! A simple text request: ;

	request("Enter A or B:","A",
	   textinput(t,t = "A" OR t = "B" OR t = "a" OR t = "b"),
	   "? Answer A or B.",nohelp);

	! The user may define his own boolean procedure for input
	  validation if more complicated tests are necessary.;

	GO TO start;	! Will restart from SAFEIO prefix beginning;
			! START is a SAFEIO label located just
			! in front of INNER.;

	! If label EOF exists, End-of-file on SYSIN (=^Z)
	! will jump to this label. If not existing in the
	! user program, the safeio block will terminate
	! through an internal safeio jump.
	! NOTE! Once Sysin.Endfile is TRUE, there can be no
	! more input on Sysin!. This mechanism will only work
	! for safeio prefixed blocks (i.e. NOT using NEW SAFEI(O)).;

    END of safeio block;

END of program;

At any question the user may input one of the SAFEIO commands:

?         gives help information.

!         FOLLOWED by:

*         changes the switch: Display-prompting-question.
/         changes the switch: Display-default-value.
=         changes the switch: Display-input (+ the *- and /-switches).
[         changes the switch: Trace (file messages).
+         closes and reopens current recording file in append mode.
;         treats line as a comment.
%         calls special procedure.
&         followed by input overrides validity test.
<FIL.EXT  opens new input file in waiting mode. Default extension =.saf
_         continues input in nowait mode.
<         closes current input file.
^         closes all active input files.
_FIL.EXT  opens new input file in nowait mode. Default extension =.saf
>FIL.EXT  opens new recording file. Default extension =.saf
>         closes current recording file.
?         prints this text.

Anything else following ! is just displaying current question.

The != command will always change the values of the switches
Display-prompting-question and Display-default-value to the same value
as the switch Display-input.

Note that the !& facility may be switched off by calling
the procedure NOOVERRIDE.

The !% facility gives the programmer the possibility to declare his
own procedure SPECIAL (with exactly that name and without parameters)
which will be called when the user responds with !%. It is
possible to interpret the information following the !% in the
procedure, thereby expanding the power of the SAFEIO - ! commands.
See SAFEIO.MAN for further information on SAFEIO attributes.

If you are using SAFEIO by INSPECT it is no use specifying any
initial recording file, since it will be immediately closed. This
is because the INNER in SAFEIO will be passed. In order to
close all possible open SAFEIO files, end the connection block with
a call of the SAFEIO procedure closefiles. I.e. :

BEGIN   EXTERNAL declarations.....;

    INSPECT NEW SAFEIO("","") DO	! Default language is english ;

    BEGIN .... using safeio ......

END program

By substituting the class SAFEIO by CLASS SAFEI (with the language
parameter only) the facilities numbered 1 to 6 will still be present
while the file handling facilities will absent. The class SAFEI
will require about 2/5 of the memory of SAFEIO.

By substituting to SAFMIN still more SAFEIO facilities
are excluded. See SAFMIN.HLP. Size of SAFMIN is about 1/2 of SAFEI.

The three classes SIMMIN, SIMEI and SIMEIO are identical with SAFMIN,
SAFEI and SAFEIO respectively in all respects but prefixed with

	[End of SAFEIO.HLP]