fp1/week2/mart/StdT.icl

   1 implementation module StdT
   2
   3 import StdEnv
   4
   5 ::      T = {m :: Int, s :: Int}
   6
   7 instance ==     T where
   8         == a b = a.m == b.m && a.s == b.s
   9 instance <      T where
  10         < a b = a.m < b.m || a.s == b.s && a.s < b.s
  11
  12 instance zero   T where
  13         zero = {m=zero, s=zero}
  14 instance +      T where
  15         + a b = fromInt (toInt a + toInt b)
  16 instance -      T where
  17         - a b = fromInt (toInt a - toInt b)
  18
  19 instance toInt  T where
  20         toInt a = a.m*60 + a.s
  21 instance fromInt        T where
  22         fromInt a
  23         | a<0 = zero
  24         | otherwise = {m=a/60, s=a rem 60}
  25
  26 instance toString       T where
  27         toString {m=ms, s=0} = toString ms +++ ":00"
  28         toString {m=ms, s=ss}
  29         | ss < 10 = toString ms +++ ":0" +++ toString ss
  30         | otherwise = toString ms +++ ":" +++ toString ss
  31
  32 instance fromString     T where
  33         fromString a
  34         | a.[size a - 3] == ':' = {m = toInt (a % (0, (size a) - 4)), s = toInt (a % ((size a) - 2, size a))}
  35         | otherwise = zero