langs a-z

Task/Hailstone-sequence/UNIX-Shell/hailstone-sequence-1.sh

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+#!/bin/bash
+# seq is the array genereated by hailstone
+# index is used for seq
+declare -a seq
+declare -i index
+
+# Create a routine to generate the hailstone sequence for a number
+hailstone () {
+  unset seq index
+  seq[$((index++))]=$((n=$1))
+  while [ $n -ne 1 ]; do
+    [ $((n % 2)) -eq 1 ] && ((n=n*3+1)) || ((n=n/2))
+    seq[$((index++))]=$n
+  done
+}
+
+# Use the routine to show that the hailstone sequence for the number 27
+# has 112 elements starting with 27, 82, 41, 124 and ending with 8, 4, 2, 1
+i=27
+hailstone $i
+echo "$i: ${#seq[@]}"
+echo "${seq[@]:0:4} ... ${seq[@]:(-4):4}"
+
+# Show the number less than 100,000 which has the longest hailstone
+# sequence together with that sequences length.
+# (But don't show the actual sequence)!
+max=0
+maxlen=0
+for ((i=1;i<100000;i++)); do
+  hailstone $i
+  if [ $((len=${#seq[@]})) -gt $maxlen ]; then
+    max=$i
+    maxlen=$len
+  fi
+done
+
+echo "${max} has a hailstone sequence length of ${maxlen}"

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

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+# 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."

Task/Hailstone-sequence/UNIX-Shell/hailstone-sequence-3.sh

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+# Outputs a hailstone sequence from !:1, with one element per line.
+# Clobbers $n.
+alias hailstone eval \''@ n = \!:1:q		\\
+	echo $n					\\
+	while ( $n != 1 )			\\
+		if ( $n % 2 ) then		\\
+			@ n = 3 * $n + 1	\\
+		else				\\
+			@ n /= 2		\\
+		endif				\\
+		echo $n				\\
+	end					\\
+'\'
+
+set sequence=(`hailstone 27`)
+echo "Hailstone sequence from 27 has $#sequence elements:"
+@ i = $#sequence - 3
+echo "  $sequence[1-4] ... $sequence[$i-]"
+
+# hailstone-length $i
+#   acts like
+# @ len = `hailstone $i | wc -l | tr -d ' '`
+#   but without forking any subshells.
+alias hailstone-length eval \''@ n = \!:1:q	\\
+	@ len = 1				\\
+	while ( $n != 1 )			\\
+		if ( $n % 2 ) then		\\
+			@ n = 3 * $n + 1	\\
+		else				\\
+			@ n /= 2		\\
+		endif				\\
+		@ len += 1			\\
+	end					\\
+'\'
+
+@ i = 1
+@ max = 0
+@ maxlen = 0
+while ($i < 100000)
+	# XXX - I must run hailstone-length in a subshell, because my
+	# C Shell has a bug when it runs hailstone-length inside this
+	# while ($i < 1000) loop: it forgets about this loop, and
+	# reports an error <<end: Not in while/foreach.>>
+	@ len = `hailstone-length $i; echo $len`
+	if ($len > $maxlen) then
+		@ max = $i
+		@ maxlen = $len
+	endif
+	@ i += 1
+end
+echo "Hailstone sequence from $max has $maxlen elements."