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datatype 'a Option = None | Some of 'a
fun digit n = chr(ord #"0" + n)
fun digits(n,acc) =
if n >=0 andalso n<=9 then digit n:: acc
else digits (n div 10, digit(n mod 10) :: acc)
fun toString(n) = implode(digits(n,[]))
fun writeln s = print(s^"\n")
fun percent(i: int, j: int)(*:int*) =
floor((real i * 100.0)/real j)
(* seek: (char -> bool) -> instream -> string list:
seek(pred)(is) returns the list of characters obtained
by reading from up to and including the first character
which satisfies "pred". (If no such character exists, the
empty list is returned.
*)
exception Impossible
fun seek (pred: char -> bool) (is: TextIO.instream): char list =
let fun readLoop() =
(case explode (TextIO.inputN(is, 1)) of
[] => []
| [char] => char :: (if pred char then []
else readLoop())
| _ => (print "lib.seek: impossible"; raise Impossible))
in readLoop()
end
fun readLn(is) = seek(fn ch => ch = #"\n")is
(* dropwhile: ('a -> bool) -> 'a list -> 'a list; endomorphic *)
fun dropwhile pred l =
let fun drop_loop (l as []) = l
| drop_loop (l as x::xs) =
if pred x then drop_loop xs else l
in drop_loop l
end
(* takewhile: ('a -> bool) -> 'a list -> 'a list; exomorphic *)
fun takewhile pred l =
let fun take_loop [] = []
| take_loop (l as x::xs) =
if pred x then x:: take_loop xs else []
in take_loop l
end
fun isSpace(ch:char) =
ch = #" " orelse ch = #"\t" orelse ch = #"\n"
(* orelse ch= "\f" orelse ch = "\r" orelse ch = "\v"*)
fun readWord(is): string Option =
case
implode(takewhile(not o isSpace)
(dropwhile isSpace (readLn is)))
of "" => None
| word => Some word
|
