[comp.lang.pascal] VAX Pascal Question. Somebody...

bbehrmann@desire.wright.edu (05/10/91)

	I've never used VAX Pascal before, stick with TP, but I am trying
to program something on a VMS system and am in need of a RANDOM number
function, and a function that allows you to execute VAX commands.  (Some
type of SHELL)  If anyone happens to know the answer, I'd greatly appriciate
it if you would let me know!!
Thanks!!
Talk to you later!!
 
                                  -Barry-
                        <BBEHRMANN@DESIRE.WRIGHT.EDU>

doody@shrnew.enet.dec.com (05/15/91)

In article <1991May9.141955.3561@desire.wright.edu>, bbehrmann@desire.wright.edu writes:
|>
|>	I've never used VAX Pascal before, stick with TP, but I am trying
|>to program something on a VMS system and am in need of a RANDOM number
|>function, and a function that allows you to execute VAX commands.  (Some
|>type of SHELL)  If anyone happens to know the answer, I'd greatly appriciate
|>it if you would let me know!!
|>Thanks!!
|>Talk to you later!!
|> 
|>                                  -Barry-
|>                        <BBEHRMANN@DESIRE.WRIGHT.EDU>
|>

Well, I have used VAX Pascal and TP. Both are great at what they do. For VAX
Pascal, You want to use the VMS RTL (run-time libraries). See $HELP RTL LIB$
and $ HELP RTL MTH$  (or much better, the hardcopy if you got em). 

For a 'shell' (really a command line interpreter in VMS lingo) You'll want to
use LIB$SPAWN. There are lots of options for LIB$SPAWN. You'll have to read the
docs for them all. The following fragment shows an example I've used to mail a
message (before the days of callable mail). Any DCL command could be used. 
Also you can specify a command file ( script ) to run instead of just a single 
command.

[ INHERIT('sys$library:starlet',
	  'sys$library:pascal$lib_routines' )]   
                  { need to INHERIT the routine declaration }

[...]

    VAR
	spawn_command		: varying [255] of char;
	spawn_status		: [volatile] unsigned; 
 { [volatile] because LIB$SPAWN is going to modify it behind Pascal's back...}

[...]

    spawn_status := 0;
    WRITEV( spawn_command, '$ mail/noself ', my_filename, mail_address );
    lib$spawn (
        command_string := spawn_command,
        completion_status_address := address(spawn_status) );
    if not odd( spawn_status )
    then
	begin
	{ error during the DCL command }
	end;



Here's a little example for random number generation. You'll have to come up
with an initial seed. Maybe generated from the current time or something.

[ INHERIT('sys$library:pascal$mth_routines' )]   

PROGRAM random ( OUTPUT );

    VAR
	random_number	: REAL;
	seed		: UNSIGNED;
	loop		: INTEGER;

    BEGIN
    {seed := routine_to_get_seed;}
    seed := 826495832;   { for example to run }
    FOR loop := 1 TO 10 DO
	BEGIN
	random_number := MTH$RANDOM ( seed );	
	WRITELN( 'Seed is ', Seed:11,'   random is ', random_number:0:11 );
	END;
    END.