#! /bin/sh

# factorial -- computes factorial 
# $Id: factorial,v 2.2 1998/07/09 02:40:14 cdua Exp cdua $
# Carlos Duarte, 960719/971116

# usage: ./fact.b 3 5 12 44 ... 

#trap -- 'rm -f /tmp/xpto' EXIT SIGINT

USAGE="\
usage: $0 [-h] [-n] n1 [n2 ...]

  -h      this help
  -n      no op
"
while : ; do
	case x"$1" in 
	x-h)	echo "$USAGE"; exit 1 ;;
	x-n)	CMD=cat ;; 
	x--)	shift; break ;;
	x-?)	echo "invalid option -- `echo $1|cut -c2-`"
		echo "$USAGE"; exit 1 ;;
	*)	break ;;
	esac
	shift
done

# if _must_ accept on extra argument after options
if test $# -eq 0; then echo "$USAGE"; exit 1; fi

: ${CMD=bc}

bc <<eof
`echo $* 0 | awk '{for (i=1; i<=NF; i++) print "a[",i,"]=",$i,";"; }'`

c[1]=1; 

# compute factorial of x; uses c[1-x] for cache
define f (x) {
	auto r

	if (c[x]) return (c[x]); 
	r=x*f(x-1);
	c[x]=r;
	return (r);
}

for (i=1; a[i]; i++) 
	print a[i], "! =", f(a[i]), "\n"
quit
eof