urbit/pkg/arvo/sur/plum.hoon

^?  |%
::
+$  tile  ::  XX: ?@(knot (pair styl knot))
          ::
          cord
::
::  A `plum` is the intermediate representation for the pretty-printer. It
::  encodes hoon-shaped data with the least amount of structured needed
::  for formating.
::
::  A `plum` is either a
::
::  - `cord`: A simple cord
::  - `[%para *]`: A wrappable paragraph.
::  - `[%tree *]`: A formatted plum tree
::  - `[%sbrk *]`: An indication of a nested subexpression.
::
::  The formatter will use the tall mode unless:
::
::    - A plum has only a `wide` style.
::    - The plum is in `%sbrk` form and its subplum (`kid`), when
::      formatted in wide mode, can fit on a single line.
::
+$  plum
  $@  cord
  $%  [%para prefix=tile lines=(list @t)]
      [%tree fmt=plumfmt kids=(list plum)]
      [%sbrk kid=plum]
  ==
::
::  A `plumfmt` is a description of how to render a `plum`. A `plumfmt`
::  must include a `wide`, a `tall`, or both.
::
::  A `wide` is a description of how to render a plum in a single
::  line. The nested (`kids`) sub-plums will be interleaved with `delimit`
::  strings, and, if `enclose` is set, then the output will be enclosed
::  with `p.u.enclose` and `q.u.enclose`.
::
::  For example, to build a plumfmt for string literals, we could write:
::
::      [wide=[~ '' [~ '"' '"']] tall=~]
::
::  A `tall` is a description of how to render a plum across multiple
::  lines. The output will be prefixed by `intro`, suffixed by
::  `final.u.indef`, and each subplum prefixed by `sigil.u.indef`.
::
::  For example, to build a plumfmt for cores, we could write:
::
::      [wide=~ tall=`['' `['++' '--']]]
::
+$  plumfmt
  $:  wide=(unit [delimit=tile enclose=(unit (pair tile tile))])
      tall=(unit [intro=tile indef=(unit [sigil=tile final=tile])])
  ==
--