?RCS: $Id: randfunc.U,v 3.0 1993/08/18 12:09:39 ram Exp $
?RCS:
?RCS: Copyright (c) 1991-1993, Raphael Manfredi
?RCS: 
?RCS: You may redistribute only under the terms of the Artistic Licence,
?RCS: as specified in the README file that comes with the distribution.
?RCS: You may reuse parts of this distribution only within the terms of
?RCS: that same Artistic Licence; a copy of which may be found at the root
?RCS: of the source tree for dist 3.0.
?RCS:
?RCS: $Log: randfunc.U,v $
?RCS: Revision 3.0  1993/08/18  12:09:39  ram
?RCS: Baseline for dist 3.0 netwide release.
?RCS:
?X:
?X:	This is the new unit that should be used when random
?X:	functions are to be used. It thus makes randbits.U obsolete.
?X:
?MAKE:randfunc mrand seedfunc nrandbits: cat +cc rm test Myread Csym
?MAKE:	-pick add $@ %<
?S:randfunc:
?S:	Indicates the name of the random number function to use.
?S:	Values include drand48, random, and rand. In C programs,
?S:	the 'nrand' macro is defined to generate uniformly distributed
?S:	random numbers over the range [0., 1.] (see mrand and nrand).
?S:.
?S:mrand:
?S:	Indicates the macro to be used to generate normalized
?S:	random numbers.  Uses randfunc, often divided by
?S:	(double) ((1 << nrandbits) -1) in order to normalize the result.
?S:	In C programs, the macro 'nrand' is maped on mrand.
?S:.
?S:seedfunc:
?S:	Indicates the random number generating seed function.
?S:	Values include srand48, srandom, and srand.
?S:.
?S:nrandbits:
?S:	Indicates how many bits are produced by the function used to
?S:	generate normalized random numbers.
?S:.
?C:nrand:
?C:	This macro is to be used to generate uniformly distributed
?C:	random numbers over the range [0., 1.].
?C:.
?C:seednrand:
?C:	This symbol defines the macro to be used in seeding the
?C:	random number generator (see nrand).
?C:.
?H:#define nrand()		$mrand		/**/
?H:#define seednrand(x)	$seedfunc(x)	/**/
?H:.
?T:cont val
: How can we generate normalized random numbers ?
echo " "
case "$randfunc" in
'')
	if set drand48 val -f; eval $csym; $val; then
		dflt="drand48"
		echo "Good, found drand48()." >&4
	elif set random val -f; eval $csym; $val; then
		dflt="random"
		echo "OK, found random()." >&4
	else
		dflt="rand"
		echo "Yick, looks like I have to use rand()." >&4
	fi
	echo " "
	;;
*)
	dflt="$randfunc"
	;;
esac
cont=true
while $test "$cont"; do
	rp="Use which function to generate random numbers?"
	. ./myread
?X: Invalidates nrandbits if the answer is not the default so
?X:	that the value stored in config.sh will not be used when
?X:	we change our random function.
	if $test "$ans" = "$dflt"; then
		: null
	else
		nrandbits=''
	fi
	randfunc="$ans"
	if set $ans val -f; eval $csym; $val; then
		cont=''
	else
		dflt=n
		rp="Function $ans does not exists. Use that name anyway?"
		. ./myread
		dflt=rand
		case "$ans" in
			[yY]*) cont='';;
		esac
	fi
	case "$cont" in
	'')
		case "$randfunc" in
		drand48)
			mrand="drand48()"
			seedfunc="srand48"
			;;
		rand*)
			case "$nrandbits" in
			'')
echo "Checking to see how many bits your $randfunc() function produces..." >&4
			$cat >try.c <<EOCP
#include <stdio.h>
main()
{
	register int i;
	register unsigned long tmp;
	register unsigned long max = 0L;
	extern long random();

	for (i = 1000; i; i--) {
		tmp = (unsigned long)$randfunc();
		if (tmp > max) max = tmp;
	}
	for (i = 0; max; i++)
		max /= 2;
	printf("%d\n",i);
}
EOCP
			if $cc try.c -o try >/dev/null 2>&1 ; then
			dflt=`try`
			else
			dflt='?'
			echo "(I can't seem to compile the test program...)"
			fi
			;;
			*)
				dflt="$nrandbits"
				;;
			esac
			rp="How many bits does your $randfunc() function produce?"
			. ./myread
			nrandbits="$ans"
			$rm -f try.c try
			mrand="($randfunc() / (double) ((1 << $nrandbits) -1))"
			seedfunc="srand"
			;;
?X:	The following is provided just in case...
		*)
			dflt="31"
			rp="How many bits does your $randfunc() function produce?"
			. ./myread
			nrandbits="$ans"
			seedfunc="s$randfunc"
			mrand="($randfunc() / (double) ((1 << $nrandbits) -1))"
			if set $seedfunc val -f; eval $csym; $val; then
				echo "(Using $seedfunc() to seed random generator)"
			else
				echo "(Warning: no $seedfunc() to seed random generator)"
				seedfunc=rand
			fi
			;;
		esac
		;;
	esac
done