!:
:-  %say
|=  *
:-  %noun
=-  "hello, world"
|%
+$  scan  [=loop=(map =@ud =xray) =xray]
+$  xray
  $~  %noun
  $@  $?  %noun
          %void
      ==
  $%  ::  %bark: atom selection
      ::
      [%bark =(map atom aura)]
      ::  %bush: head-of-cell superposition
      ::
      [%bush wide=xray tall=xray]
      ::  %cell: ordered pair
      ::
      [%cell head=xray tail=xray]
      ::  %core: functional attribute battery
      ::
      [%core =vair =xray =(map term (map term xray))]
      ::  %face: namespace
      ::
      [%face =term =xray]
      ::  %fork: disordered superposition
      ::
      [%fork =(set xray)]
      ::  %hint: context-preserving type hint
      ::
      [%hint [=type =note] =xray]
      ::  %knot: recursion root
      ::
      [%knot =(set @ud) =xray]
      ::  %loop: recursion point
      ::
      [%loop index=@ud]
      ::  %rock: constant
      ::
      [%rock =atom =aura]
      ::  %root: atom/cell superposition
      ::
      [%root flat=xray deep=xray]
      ::  %sand: variable atom
      ::
      [%sand =aura]
      ::  %wood: tagged superposition
      ::
      [%wood =(map atom (pair aura xray))]
  ==
++  foo
  |=  bar=xray
  !!
--