Logic Gates in bash, based on @cassidoo's interview question from November 11, 2019

logicgate.sh

#!/usr/bin/env bash
set -eu -o pipefail

about () {
cat <<EOF
$( basename "$0" ) by Andrew Rich <[email protected]>
Based on @cassidoo's interview question from https://tinyletter.com/cassidoo/letters/be-curious-read-widely-try-new-things-what-people-call-intelligence-just-boils-down-to-curiosity-aaron-swartz
Definition and table of logic gates: https://whatis.techtarget.com/definition/logic-gate-AND-OR-XOR-NOT-NAND-NOR-and-XNOR

EOF
}
syntax () {
cat <<EOF
Usage: $( basename "$0" ) <GATE> <VALUE1> [VALUE2]
Possible values for GATE are AND, OR, NOT, NAND, NOR, XOR, XNOR
VALUE1 (required) and VALUE2 (optional) are integers to evaluate with GATE

Examples:
$ logicGate AND 1 1
=> 1
$ logicGate NOT 1
=> 0
$ logicGate NAND 1 0
=> 1
$ logicGate NOR 0 0
=> 1

VALUE2 is ignored if the selected GATE takes only a single value.

EOF
}

if [ $# -lt 2 ]; then
	# we need at least two params
	about
	syntax
	exit 1
fi

GATE=$( tr '[:lower:]' '[:upper:]' <<< "$1" )

if [[ ${GATE} != "NOT" ]] && [[ -z ${3+x} ]]; then
	# gates other than NOT require two params
	syntax
	exit 1
fi

case $GATE in
	'AND')
		echo -e "AND $2 $3: $(( $2&$3 ))"
		;;
	'OR')
		echo -e "OR $2 $3: $(( $2|$3 ))"
		;;
	'NOT')
		echo -e "NOT $2: $(( !$2 ))"
		;;
	'NAND')
		echo -e "NAND $2 $3: $(( !($2&$3) ))"
		;;
	'NOR')
		echo -e "NOR $2 $3: $(( !($2|$3) ))"
		;;
	'XOR')
		echo -e "XOR $2 $3: $(( $2^$3 ))"
		;;
	'XNOR')
		echo -e "XNOR $2 $3: $(( !($2^$3) ))"
		;;
	*)
		echo -e "*** Error: Invalid GATE: $1\n"
		syntax
		exit 1
		;;
esac