vm_eval options.get_string options.mk "opt1" "<empty>"
vm_eval options.get_string (options.set_string options.mk "opt1" "val1") "opt1" "<empty>"
vm_eval if (options.mk = options.mk) then bool.tt else bool.ff
vm_eval if (options.mk = (options.set_string options.mk "opt1" "val1")) then bool.tt else bool.ff
vm_eval options.get_nat (options.set_nat options.mk "opt1" 10) "opt1" 0
vm_eval options.get_nat (options.set_nat options.mk "opt1" 10) "opt2" 0