?>  ?=([@ @] .)
%.  .
|=  [x=@ y=@]
=-  (add:all x y)
^=  all
=>  %164
~%  %k164  ~  ~ 
|%
++  add
  ~/  %add
  |=  [a=@ b=@]
  ^-  @
  ?:  =(0 a)  b
  $(a (dec a), b +(b))
::
++  dec
  ~/  %dec
  |=  a=@
  ?<  =(0 a)
  =+  b=0
  |-  ^-  @
  ?:  =(a +(b))  b
  $(b +(b))
--