structure OutputFN =

struct

(* rebuilding the output function from ThyOutput in order to *)

(* enable the options [gray, linenos, index]                   *)

val gray = ref false

val linenos = ref false

datatype entry = 

   No_Entry

 | Code_Entry of string

 | String_Entry of string

val index = ref No_Entry

fun string_entry s = prefix ("\\index{" ^ s ^ "}")

fun code_entry   s = prefix ("\\index{" ^ s ^ "@{\\tt\\slshape{}" ^ s ^ "}}")

fun get_word str =

let 

  fun only_letters [] = true

    | only_letters (x::xs) = 

        if (Symbol.is_ascii_blank x) then false else only_letters xs

in

  if (only_letters (Symbol.explode str)) then str

  else error ("Underspecified index entry only for single words allowed! Error with " ^ str)

end  

fun index_entry entry txt =

 case entry of

   No_Entry => I

 | String_Entry "" => string_entry (get_word (implode txt))

 | String_Entry s  => string_entry s

 | Code_Entry ""   => code_entry (get_word (implode txt))

 | Code_Entry s    => code_entry s

fun translate f = Symbol.explode #> map f #> implode;

val clean_string = translate

  (fn "_" => "\\_"

    | c => c);

fun output txt =

let

  val prts = map Pretty.str txt

in   

  prts

  |> (if ! ThyOutput.quotes then map Pretty.quote else I)

  |> (if ! ThyOutput.display then

    map (Output.output o Pretty.string_of o Pretty.indent (! ThyOutput.indent))

    #> space_implode "\\isasep\\isanewline%\n"

    #> (if ! linenos then (enclose "\\begin{linenos}%\n" "%\n\\end{linenos}") else I) 

    #> (if ! gray then (enclose "\\begin{graybox}%\n" "%\n\\end{graybox}") else I) 

    #> enclose "\\begin{isabelle}%\n" "%\n\\end{isabelle}"

    #> index_entry (!index) txt

  else

    map (Output.output o (if ! ThyOutput.break then Pretty.string_of else Pretty.str_of))

    #> space_implode "\\isasep\\isanewline%\n"

    #> enclose "\\isa{" "}"

    #> index_entry (!index) txt)

end

fun boolean "" = true

  | boolean "true" = true

  | boolean "false" = false

  | boolean s = error ("Bad boolean value: " ^ quote s);

val _ = ThyOutput.add_options

 [("gray", Library.setmp gray o boolean),

  ("linenos", Library.setmp linenos o boolean),

  ("index", Library.setmp index o String_Entry o clean_string),

  ("indexc", Library.setmp index o Code_Entry o clean_string)]

end