Unary math Towers of Hanoi in naked (D)ASH and BASH
The following solution assumes neither BASH extensions, nor any external executables. Hence it could be ran from a preboot environment like a frugal initrd. A slight compromise was to use unary math. Did you know, that you can access an animated version from Emacs by typing M-x hanoi ? pop(){ shift echo $* } top(){ echo $1 } print_towers(){ echo "a=[" $a "], b=[" $b "], c=[" $c "]" } hanoi(){ [ "$n" ] || return local ln ln=$(pop $n) n=$ln hanoi $1 $3 $2 print_towers echo "$1 -> $2" eval $2=\"$(eval top \$$1) $(echo \$$2)\" eval $1=\"$(eval pop \$$1)\" n=$ln hanoi $3 $2 $1 } main(){ a="1 2 3 4 5" b= c= n=$a hanoi a b c print_towers } main "$@"
