hex.forth

: hexchr>n ( chr -- n )
    48 over 57  between? if 48 - exit then
    65 over 70  between? if 55 - exit then
    97 over 102 between? if 87 - exit then
    -1 ;
    
: hexstr>n ( adr len -- n )
  0 >r
  begin
    dup 0 >
  while
    1 - ( len )
    r> 4 lshift >r ( acc )
    over c@ hexchr>n ( digit )
    r> + >r ( acc )
    swap 1 + swap ( address )
  repeat 
  2drop r> ;

: 0x ( <word> -- n ) word hexstr>n ;