(* Fnlib.sml. Library functions *) exception Impossible of string; fun fatalError s = raise(Impossible s); fun getOption NONE = fatalError "getOption"  | getOption (SOME a) = a; fun fst (x, y) = x;fun snd (x, y) = y; fun incr r = r := !r + 1;fun decr r = r := !r - 1; fun mapFrom f n [] = []  | mapFrom f n (x :: xs) = f n x :: mapFrom f (n+1) xs; fun map2 f [] [] = []  | map2 f (x :: xs) (y :: ys) = f x y :: map2 f xs ys  | map2 f _ _ = fatalError "map2: lists of different length"; fun appFrom f n [] = ()  | appFrom f n (x :: xs) = (f n x : unit; appFrom f (n+1) xs); fun app2 f [] [] = ()  | app2 f (x::xs) (y::ys) = (f x y : unit; app2 f xs ys)  | app2 f _ _ = fatalError "app2: lists of different length"; fun revApp f [] = ()  | revApp f (h::t) = (revApp f t;f  h); fun foldL f a [] = a  | foldL f a (x::xs) = foldL f (f x a) xs; fun foldL_zip f a [] [] = a  | foldL_zip f a (x::xs) (y::ys) = foldL_zip f (f x y a) xs ys  | foldL_zip f a _ _ = fatalError "foldL_zip: lists of different length"; fun foldL_map f g a [] = a  | foldL_map f g a (x::xs) = foldL_map f g (f (g x) a) xs; fun foldR f a [] = a  | foldR f a (x::xs) = f x (foldR f a xs); fun foldR1 f [] = fatalError "foldR1: an empty argument"  | foldR1 f [x]   = x  | foldR1 f (x::xs) = f x (foldR1 f xs); fun foldR_map f g e [] = e  | foldR_map f g e (x::xs) = f (g x) (foldR_map f g e xs); fun map_fields f [] = []  | map_fields f ((lab, t) :: xs) = (lab, f t) :: map_fields f xs; fun all_fields f [] = true  | all_fields f ((_, t) :: xs) =      (f t) andalso all_fields f xs; fun exists_field f [] = false  | exists_field f ((_, t) :: xs) =      (f t) orelse exists_field f xs; fun app_field f [] = ()  | app_field f ((_, t) :: xs) = (f t : unit; app_field f xs); fun member k [] = false  | member k (x :: xs) =    if k = x then true else member k xs; fun exists p [] = false  | exists p (a::xs) = p a orelse exists p xs; fun remove k [] = []  | remove k (x :: xs) =    if k = x then xs else x :: (remove k xs); fun drop p [] = []  | drop p (x :: xs) =    if p x then (drop p xs) else x :: (drop p xs); fun lookup k [] = raise Subscript  | lookup k ((a, v) :: xs) =    if k = a then v else lookup k xs;  (* The vector vec must be sorted *) fun binlookup (name : string) (vec : (string * 'a) Vector.vector) =    let fun search a b = 	    if a > b then raise Subscript	    else		let val i = (a+b) div 2		    val (key, v) = Vector.sub(vec, i)		in 		    if name < key      then search a (i-1)		    else if key < name then search (i+1) b		    else v		end    in search 0 (Vector.length vec - 1) end;  fun choose p [] = raise Subscript  | choose p (a::xs) =    if p a then a else choose p xs; fun find p [] = raise Subscript  | find p ((a, v) :: xs) =    if p a then v else find p xs; fun foldInt f a n = if n <= 0 then a else f n (foldInt f a (n-1)); fun duplicates [] = false  | duplicates (x :: xs) = member x xs orelse duplicates xs;fun stringToLower s =    CharVector.tabulate(size s, fn i => Char.toLower(CharVector.sub(s, i))); fun for f i j =  if i > j then () else (f i : unit; for f (i+1) j); fun zip2 [] [] = []  | zip2 [] (y :: ys) = fatalError "zip2"  | zip2 (x :: xs) [] = fatalError "zip2"  | zip2 (x :: xs) (y :: ys) = (x, y) :: zip2 xs ys;