regression/lib.sml

   1 datatype 'a Option = None | Some of 'a
   2
   3 fun digit n = chr(ord #"0" + n)
   4 fun digits(n,acc) =
   5       if n >=0 andalso n<=9 then digit n:: acc
   6       else digits (n div 10, digit(n mod 10) :: acc)
   7
   8 fun toString(n) = implode(digits(n,[]))
   9
  10 fun writeln s = print(s^"\n")
  11
  12 fun percent(i: int, j: int)(*:int*) =
  13      floor((real i * 100.0)/real j)
  14
  15 (* seek: (char -> bool) -> instream -> string list:
  16    seek(pred)(is) returns the list of characters obtained
  17    by reading from up to and including the first character
  18    which satisfies "pred". (If no such character exists, the
  19    empty list is returned.
  20 *)
  21 exception Impossible
  22 fun seek (pred: char -> bool) (is: TextIO.instream): char list =
  23   let fun readLoop() =
  24             (case explode (TextIO.inputN(is, 1)) of
  25                []  =>  []
  26              | [char] => char :: (if pred char then  []
  27                                   else readLoop())
  28              | _ => (print "lib.seek: impossible"; raise Impossible))
  29   in readLoop()
  30   end
  31
  32 fun readLn(is) = seek(fn ch => ch = #"\n")is
  33
  34 (* dropwhile: ('a -> bool) -> 'a list -> 'a list; endomorphic *)
  35 fun dropwhile pred l =
  36   let fun drop_loop (l as []) = l
  37         | drop_loop (l as x::xs) =
  38            if pred x then drop_loop xs else l
  39   in drop_loop l
  40   end
  41
  42 (* takewhile: ('a -> bool) -> 'a list -> 'a list; exomorphic *)
  43 fun takewhile pred l =
  44   let fun take_loop [] = []
  45         | take_loop (l as x::xs) =
  46            if pred x then x:: take_loop xs else []
  47   in take_loop l
  48   end
  49
  50 fun isSpace(ch:char) =
  51       ch = #" " orelse ch = #"\t" orelse ch = #"\n"
  52       (* orelse ch= "\f" orelse ch = "\r" orelse ch = "\v"*)
  53
  54 fun readWord(is): string Option =
  55   case
  56     implode(takewhile(not o isSpace)
  57             (dropwhile isSpace (readLn is)))
  58   of "" => None
  59    | word => Some word
  60
  61