This is a vocabulary for doing some basic operations on unsigned
numbers.

~~~
:u:patch (n-n)
  dup n:negative?
  [ #2147483647 n:add n:inc swap #-2147483648 n:sub n:add ] if ;

:u:add (nn-n)  n:add u:patch ;
:u:sub (nn-n)  n:sub u:patch ;
:u:mul (nn-n)  n:mul u:patch ;
:u:div (nn-n)
  dup n:zero? [ drop-pair n:MAX ] [ n:div u:patch ] choose ;
:u:mod (nn-n)
  dup n:zero? [ drop-pair n:MAX ] [ n:mod u:patch ] choose ;

:u:eq? (nn-f)   or not ;
:u:-eq? (nn-f)  u:eq? not ;
:u:lt? (nn-f)   over or and n:negative? ;
:u:gt? (nn-f)   tuck or and n:negative? ;
~~~