langs a-z

Task/Hailstone-sequence/UNIX-Shell/hailstone-sequence-2.sh

@@ -0,0 +1,30 @@
+# Outputs a hailstone sequence from $1, with one element per line.
+# Clobbers $n.
+hailstone() {
+	n=`expr "$1" + 0`
+	eval "test $? -lt 2 || return $?"  # $n must be integer.
+
+	echo $n
+	while test $n -ne 1; do
+		if expr $n % 2 >/dev/null; then
+			n=`expr 3 \* $n + 1`
+		else
+			n=`expr $n / 2`
+		fi
+		echo $n
+	done
+}
+
+set -- `hailstone 27`
+echo "Hailstone sequence from 27 has $# elements:"
+first="$1, $2, $3, $4"
+shift `expr $# - 4`
+echo "  $first, ..., $1, $2, $3, $4"
+
+i=1 max=0 maxlen=0
+while test $i -lt 1000; do
+	len=`hailstone $i | wc -l | tr -d ' '`
+	test $len -gt $maxlen && max=$i maxlen=$len
+	i=`expr $i + 1`
+done
+echo "Hailstone sequence from $max has $maxlen elements."