Re: (no subject)

25 Feb 2002


      At 2002-02-24 22:46, Tom Bevan wrote:
...
I've come across this sort of data constructor below many times but I'm
not really sure how to use it. Can someone please point me to the right
section in the documentation?
http://haskell.org/onlinereport/decls.html#sect4.2.1
"Labelled Fields"
...
In particular, I want to know how to create a calendar time and how to
access the fields .
Tom
data CalendarTime = CalendarTime {
      ctYear   :: Int,
       	ctMonth  :: Month,
       	ctDay, ctHour, ctMin, ctSec  :: Int,
      ctPicosec :: Integer,
      ctWDay    :: Day,
      ctYDay       :: Int,
      ctTZName   :: String,
      ctTZ          :: Int,
      ctIsDST :: Bool
  } deriving (Eq, Ord, Read, Show)
Basically it's equivalent to this:

data CalendarTime = CalendarTime Int Month Int Int Int Int Integer Day 
Int String Int Bool deriving (Eq, Ord, Read, Show);

ctYear (CalendarTime x _ _ _ _ _ _ _ _ _ _ _) = x;
ctMonth (CalendarTime _ x _ _ _ _ _ _ _ _ _ _) = x;
ctDay (CalendarTime _ _ x _ _ _ _ _ _ _ _ _) = x;
etc.

...but you can also use the labelled fields to construct:

CalendarTime
    {
    ctYear = 2002,
    ctMonth = 2,
    ...
    }


-- 
Ashley Yakeley, Seattle WA