structure InteractionMode:
sig
  datatype interaction = BATCHMODE | NONSTOPMODE | SCROLLMODE | ERRORSTOPMODE
  val fromString: string -> interaction option
  val toString: interaction -> string
end =
struct
  datatype interaction = BATCHMODE | NONSTOPMODE | SCROLLMODE | ERRORSTOPMODE
  fun fromString "batchmode" = SOME BATCHMODE
    | fromString "nonstopmode" = SOME NONSTOPMODE
    | fromString "scrollmode" = SOME SCROLLMODE
    | fromString "errorstopmode" = SOME ERRORSTOPMODE
    | fromString _ = NONE
  fun toString BATCHMODE = "batchmode"
    | toString NONSTOPMODE = "nonstopmode"
    | toString SCROLLMODE = "scrollmode"
    | toString ERRORSTOPMODE = "errorstopmode"
end;

structure ShellEscape:
sig
  datatype shell_escape = ALLOWED | RESTRICTED | FORBIDDEN
end =
struct datatype shell_escape = ALLOWED | RESTRICTED | FORBIDDEN end;

structure OutputFormat:
sig
  datatype format = PDF | DVI
  val fromString: string -> format option
end =
struct
  datatype format = PDF | DVI
  fun fromString "pdf" = SOME PDF
    | fromString "dvi" = SOME DVI
    | fromString _ = NONE
end;