{
{-# LINE 210 "Slides.ltx" #-}
class Format a where
 noDoc    ::                 a
 text     :: String     ->   a
 line     ::                 a
 (<>)     :: a     -> a  ->  a
 group    :: a           ->  a
 nest     :: Int   -> a  ->  a
{-# LINE 236 "Slides.ltx" #-}
data Tree = Tree String [Tree]
{-# LINE 241 "Slides.ltx" #-}
ex = Tree "aaa"  [Tree "bbbb"  [Tree "ccc" []
                               ,Tree "dd"  []
                               ]
                 ,Tree "eee"   []
                 ,Tree "ffff"  [Tree "gg"  []
                               ,Tree "hhh" []
                               ,Tree "ii"  []
                               ]
                 ]
{-# LINE 268 "Slides.ltx" #-}
showTree     (Tree s ts)  =  group   
                           (  text s <> nest (length s) 
                              (showBracket ts)
                           )
showBracket  []           =   noDoc
showBracket  ts           =   text  "[" 
                           <>  nest 1 (showTrees ts) 
                           <>  text  "]"
showTrees    [t]          =   showTree t
showTrees    (t:ts)       =   showTree t  
                           <>  text "," <> line 
                           <>  showTrees ts
{-# LINE 324 "Slides.ltx" #-}
type Width   = Int
w  ::  Width
{-# LINE 328 "Slides.ltx" #-}
w  =   20
{-# LINE 349 "Slides.ltx" #-}
type Fit          =  Bool             
{-# LINE 351 "Slides.ltx" #-}
type Space        =  Int               
{-# LINE 353 "Slides.ltx" #-}
type Hp           =  Int
{-# LINE 355 "Slides.ltx" #-}
type Indent        =  Int
{-# LINE 357 "Slides.ltx" #-}
type Formatter1    =  Fit  -> Space -> Hp -> Indent -> (Space, Hp, Result)
{-# LINE 382 "Slides.ltx" #-}
type Result = String -> String
toSeq  s = s []
{-# LINE 655 "Slides.ltx" #-}
type FittingChildren1  =  Fits -> Fits      --  efficient list implementation
{-# LINE 657 "Slides.ltx" #-}
type Mep               =  Int
{-# LINE 659 "Slides.ltx" #-}
data Q                 =  Q  Mep  FittingChildren1
{-# LINE 661 "Slides.ltx" #-}
type Fits   = [Bool]
type Path              =  [Q]
{-# LINE 671 "Slides.ltx" #-}
enterGroup   ::   Mep  ->     Path          ->      Path
leaveGroup   ::   Hp   ->  (  Path,  Fits)  ->   (  Path, Fits)
prune        ::   Hp   ->  (  Path,  Fits)  ->   (  Path, Fits)
{-# LINE 682 "Slides.ltx" #-}
enterGroup mep p  = p ++ [Q mep id]
{-# LINE 699 "Slides.ltx" #-}
leaveGroup  hp pa@(p, a)     =  
  case p of
  []                ->  pa
{-# LINE 703 "Slides.ltx" #-}
  [Q mep c]         ->  ([]    ,  (mep<=hp): c a )
{-# LINE 713 "Slides.ltx" #-}
  pp                -> let (Q mep2 c2:(Q mep1 c1:qq)) = reverse pp
                       in (  reverse  (Q mep1 (c1.((hp <= mep2):).c2):qq)
                          ,  a          
                          )

{-# LINE 724 "Slides.ltx" #-}
prune hp pa@(p,a)   =  
  case  p of
  []                            ->  pa
  (Q mep   c:p')  | hp <= mep   ->  pa
                  | True        ->  let   (p''  ,              rest ) = prune hp (p', a) 
                                    in    (p''  ,   False: c   rest )
}
{-# LINE 903 "Slides.ltx" #-}
DATA Doc
|  NoDoc
|  Text t:String
|  Line
|  Besides  l:  Doc   r:  Doc
|  Group    d:  Doc
|  Nest     j:  Int   d:  Doc

{-# LINE 913 "Slides.ltx" #-}
ATTR Doc [|res:String|]
{-# LINE 916 "Slides.ltx" #-}
SEM Doc 
|  Text      lhs.res        =  @t   ++  @lhs.res
|  Line      lhs.res        =  @lr  
|  Besides   r.res          =           @lhs.res
             l.res          =           @r.res
             lhs.res        =           @l.res

{-# LINE 928 "Slides.ltx" #-}
SEM Doc [|h:Int|]
|  Text      lhs.h          =  @l   +    @lhs.h
             loc.l          =  length @t
|  Line      lhs.h          =  1    +    @lhs.h

{-# LINE 937 "Slides.ltx" #-}
SEM Doc [|s:Int|]
|  Text      lhs.s          =  @lhs.s  -  @l
|  Line      lhs.s          =  @lhs.s  -  @ls
             loc.(lr, ls)   =  newLine (head @lhs.f) @lhs.s @lhs.i @lhs.res
{
newLine  True   s     i  rest =  ( (' ':rest)                 , s - 1  )
newLine  False  s     i  rest =  ((('\n':replicate  i ' ')++rest)  , w - i  )
}
{-# LINE 945 "Slides.ltx" #-}
SEM Doc [|f:Fits|]
|  Group     d.f            =  tail (@lhs.f)
             lhs.f          =  head @lhs.f:tail @d.f
{-# LINE 953 "Slides.ltx" #-}
SEM Doc [i: Int||]
|  Nest      d.i            = @lhs.i + @j
{-# LINE 958 "Slides.ltx" #-}
SEM Doc [| future: {[Int]} |]
|  Text      lhs.future     =  length @t : @lhs.future
|  Line      lhs.future     =  []
|  Besides   r.future       =  @lhs.future
             l.future       =  @r.future
             lhs.future     =  @l.future

{-# LINE 971 "Slides.ltx" #-}
ATTR Doc [|p:Path a:Fits|]
{-# LINE 977 "Slides.ltx" #-}
SEM Doc 
|  Line       loc.(p,a)     =  foldr prune (@lhs.p, @lhs.a) (1: @lhs.future )  
{-# LINE 984 "Slides.ltx" #-}
|  Besides    r.a           =  @lhs.a
              l.a           =  @r.a
              lhs.a         =  @l.a
{-# LINE 993 "Slides.ltx" #-}
|  Group      d.p           =  enterGroup       (@lhs.h + @lhs.s)  @lhs.p 
              loc.(p,a)     =  leaveGroup       @d.h               (@d.p, @lhs.a)
              lhs.a         =  @d.a

{-# LINE 1000 "Slides.ltx" #-}
DATA Root [||res: String]
|  Root d:Doc

SEM Root
|  Root      d.s            =  w
             d.res          =  []
             d.f            =  False: @d.a
             d.h            =  0

             d.i            =  0
             d.future       =  []
             d.p            =  []
             d.a            =  []