🚀 go-pugleaf

In article <1992Sep3.201023.6191@tom.rz.uni-passau.de>, baier@forwiss.uni-passau.de (Joern Baier) writes:
> For an application I need the time and date in Quintus Prolog. I wrote a
> small predicate date/1 but I'm not content with it, because I have to
> create an extra file.

It's already in the library.
Pick up a copy of the manual, and look in the index.
(You do not need a paper copy of the manual, the on-line help system
has all the same information.)
I find, in my copy of the manual:
	"date -- library package, H-122"
You can also find this in the table of contents, where I find
	"H.11: MIscellaneous Packages ...
	  H.11-2: date.{c,pl}... H-122"

The simplest method is
	?- use_module(library(date), [date/1]).
	?- date(TodaysDate).
	TodaysDate = date(1992,8,9).
	/* Month numbers run from 0 to 11 for compatibility with ANSI C */


> How can I get a random number in PROLOG to create
> unique file names?

It's in the library.  In fact, it's library(random).  See the "Abstracts"
section in the library manual.  But if you want to generate unique file
names, random numbers are not really the way to go.  You want to use whatever
your operating system gives us, e.g. tmpnam() in UNIX.

> The main problem is that 'unix(system(date))' sends its output directly
> to the user, regardless of the current output.

Because that is what it is supposed to do.  unix(system('command'))
does exactly what system("command") would do in C, namely run the command
with the command's input coming from _STANDARD_ input and the command's
output going to _STANDARD_ output (not necessarily the terminal).

If you want to get the output of a command, what you want is 

	?- use_module(library(pipe), [popen/3]).
	?- popen(date, read, Stream),
	   read_whatever_you_want_to_from(Stream),
	   close(Stream).

This is just like popen() in UNIX+C, and it's in the "abstracts" section
of the library manual.
-- 
You can lie with statistics ... but not to a statistician.