needs lib/struct
unit emul/cpu

struct CPU {
  uint mem( ;
  method step halted? ;
}

: stepN ( n cpu -- )
  >r begin ?dup while V1 step V1 halted? not while repeat then rdrop ;
: run ( cpu -- ) begin dup step dup halted? until drop ;
: newcpu ( 'halted? 'step mem( -- cpu ) 3 n,@ ;