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<title>The Haskell 98 Library Report: Dates and Times</title>
<body bgcolor="#ffffff"> <i>The Haskell 98 Library Report</i><br> <a href="index.html">top</a> | <a href="system.html">back</a> | <a href="locale.html">next</a> | <a href="libindex.html">contents</a> <br><hr>
<a name="time"></a><a name="sect14"></a>
<h2>14<tt> </tt>Dates and Times</h2>
<p>
<table border=2 cellpadding=3>
<tr><td>
<tt><br>
module Time (<br>
ClockTime, <br>
Month(January,February,March,April,May,June,<br>
July,August,September,October,November,December),<br>
Day(Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday),<br>
CalendarTime(CalendarTime, ctYear, ctMonth, ctDay, ctHour, ctMin,<br>
ctPicosec, ctWDay, ctYDay, ctTZName, ctTZ, ctIsDST),<br>
TimeDiff(TimeDiff, tdYear, tdMonth, tdDay, tdHour,<br>
tdMin, tdSec, tdPicosec),<br>
getClockTime, addToClockTime, diffClockTimes,<br>
toCalendarTime, toUTCTime, toClockTime,<br>
calendarTimeToString, formatCalendarTime ) where<br>
<br>
import Ix(Ix)<br>
<br>
data ClockTime = ... -- Implementation-dependent<br>
instance Ord ClockTime where ...<br>
instance Eq ClockTime where ...<br>
<br>
data Month = January | February | March | April<br>
| May | June | July | August<br>
| September | October | November | December<br>
deriving (Eq, Ord, Enum, Bounded, Ix, Read, Show)<br>
<br>
data Day = Sunday | Monday | Tuesday | Wednesday | Thursday <br>
| Friday | Saturday<br>
deriving (Eq, Ord, Enum, Bounded, Ix, Read, Show)<br>
<br>
data CalendarTime = CalendarTime {<br>
ctYear :: Int,<br>
ctMonth :: Month,<br>
ctDay, ctHour, ctMin, ctSec :: Int,<br>
ctPicosec :: Integer,<br>
ctWDay :: Day,<br>
ctYDay :: Int,<br>
ctTZName :: String,<br>
ctTZ :: Int,<br>
ctIsDST :: Bool<br>
} deriving (Eq, Ord, Read, Show)<br>
<br>
data TimeDiff = TimeDiff {<br>
tdYear, tdMonth, tdDay, tdHour, tdMin, tdSec :: Int,<br>
tdPicosec :: Integer<br>
} deriving (Eq, Ord, Read, Show)<br>
</tt></td></tr></table>
<table border=2 cellpadding=3>
<tr><td>
<tt><br>
-- Functions on times<br>
getClockTime :: IO ClockTime<br>
<br>
addToClockTime :: TimeDiff -> ClockTime -> ClockTime<br>
diffClockTimes :: ClockTime -> ClockTime -> TimeDiff<br>
<br>
toCalendarTime :: ClockTime -> IO CalendarTime<br>
toUTCTime :: ClockTime -> CalendarTime<br>
toClockTime :: CalendarTime -> ClockTime<br>
calendarTimeToString :: CalendarTime -> String<br>
formatCalendarTime :: TimeLocale -> String -> CalendarTime -> String<br>
</tt></td></tr></table>
<p>
The <tt>Time</tt> library provides standard functionality for clock times,
including timezone information. It follows RFC 1129 in its use of
Coordinated Universal Time (UTC).<p>
<tt>ClockTime</tt> is an abstract type, used for the system's internal clock
time. Clock times may be compared directly or converted to a calendar
time <tt>CalendarTime</tt> for I/O or other manipulations.
<tt>CalendarTime</tt> is a user-readable and manipulable representation of
the internal <tt>ClockTime</tt> type. The numeric fields have the following
ranges.
<table border=2 cellpadding=3>
<tr><td>
<table >
<tr><td>
</td><td><I>Value</I></td><td></td><td><I>Range</I></td><td></td><td><I>Comments</I> </td></tr><tr></tr><tr><td></td><td>ctYear</td><td></td><td>-maxInt...</td><td>maxInt</td><td>Pre-Gregorian dates are inaccurate </td></tr><tr><td></td><td>ctDay</td><td></td><td>1...</td><td>31 </td></tr><tr><td></td><td>ctHour</td><td></td><td>0...</td><td>23</td></tr><tr><td></td><td>ctMin</td><td></td><td>0...</td><td>59</td></tr><tr><td></td><td>ctSec</td><td></td><td>0...</td><td>61</td><td>Allows for two Leap Seconds</td></tr><tr><td></td><td>ctPicosec</td><td></td><td>0...</td><td>(10<sup>12</sup>)-1 </td></tr><tr><td></td><td>ctYDay</td><td></td><td>0...</td><td>365</td><td>364 in non-Leap years </td></tr><tr><td></td><td>ctTZ</td><td></td><td>-89999...</td><td>89999</td><td>Variation from UTC in seconds
</td></tr></table>
</td></tr></table>
The <I>ctTZName</I> field is the name of the time zone. The <I>ctIsDST</I> field
is <tt>True</tt> if Daylight Savings Time would be in effect, and <tt>False
</tt>otherwise.
The <tt>TimeDiff</tt> type records the difference between two clock times in
a user-readable way.<p>
Function <tt>getClockTime</tt> returns the current time in its internal
representation. The expression
<tt>addToClockTime</tt> <I>d</I> <I>t</I> adds a time difference <I>d</I> and a
clock time <I>t</I> to yield a new clock time. The difference <I>d</I> may be either
positive or negative. The expression <tt>diffClockTimes</tt> <I>t1</I> <I>t2
</I>returns the difference between two clock times <I>t1</I> and <I>t2</I> as a
<tt>TimeDiff</tt>. <p>
Function <tt>toCalendarTime</tt> <I>t</I> converts <I>t</I> to a local time, modified
by the timezone and daylight savings time settings in force at the
time of conversion. Because of this dependence on the local environment,
<tt>toCalendarTime</tt> is in the <tt>IO</tt> monad.<p>
Function <tt>toUTCTime</tt> <I>t</I> converts <I>t</I> into a <tt>CalendarTime
</tt>in standard UTC format.
<tt>toClockTime</tt> <I>l</I> converts <I>l</I> into the corresponding internal
<tt>ClockTime</tt> ignoring the contents of the <I>ctWDay</I>, <I>ctYDay</I>,
<I>ctTZName</I>, and <I>ctIsDST</I> fields.<p>
Function <tt>calendarTimeToString</tt> formats
calendar times using local conventions and a formatting string.<p>
<a name="sect14.1"></a>
<h3>14.1<tt> </tt>Library <tt>Time</tt></h3>
<tt><br>
module Time (<br>
ClockTime, <br>
Month(January,February,March,April,May,June,<br>
July,August,September,October,November,December),<br>
Day(Sunday,Monday,Tuesday,Wednesday,Thursday,Friday,Saturday),<br>
CalendarTime(CalendarTime, ctYear, ctMonth, ctDay, ctHour, ctMin,<br>
ctPicosec, ctWDay, ctYDay, ctTZName, ctTZ, ctIsDST),<br>
TimeDiff(TimeDiff, tdYear, tdMonth, tdDay, <br>
tdHour, tdMin, tdSec, tdPicosec),<br>
getClockTime, addToClockTime, diffClockTimes,<br>
toCalendarTime, toUTCTime, toClockTime,<br>
calendarTimeToString, formatCalendarTime ) where<br>
<br>
import Ix(Ix)<br>
import Locale(TimeLocale(..),defaultTimeLocale)<br>
import Char ( intToDigit )<br>
<br>
data ClockTime = ... -- Implementation-dependent<br>
instance Ord ClockTime where ...<br>
instance Eq ClockTime where ...<br>
<br>
data Month = January | February | March | April<br>
| May | June | July | August<br>
| September | October | November | December<br>
deriving (Eq, Ord, Enum, Bounded, Ix, Read, Show)<br>
<br>
data Day = Sunday | Monday | Tuesday | Wednesday | Thursday <br>
| Friday | Saturday<br>
deriving (Eq, Ord, Enum, Bounded, Ix, Read, Show)<br>
<br>
data CalendarTime = CalendarTime {<br>
ctYear :: Int,<br>
ctMonth :: Month,<br>
ctDay, ctHour, ctMin, ctSec :: Int,<br>
ctPicosec :: Integer,<br>
ctWDay :: Day,<br>
ctYDay :: Int,<br>
ctTZName :: String,<br>
ctTZ :: Int,<br>
ctIsDST :: Bool<br>
} deriving (Eq, Ord, Read, Show)<br>
<br>
data TimeDiff = TimeDiff {<br>
tdYear, tdMonth, tdDay, tdHour, tdMin, tdSec :: Int,<br>
tdPicosec :: Integer<br>
} deriving (Eq, Ord, Read, Show)<br>
<br>
<br>
getClockTime :: IO ClockTime<br>
getClockTime = ... -- Implementation-dependent<br>
<br>
addToClockTime :: TimeDiff -> ClockTime -> ClockTime<br>
addToClockTime td ct = ... -- Implementation-dependent<br>
<br>
diffClockTimes :: ClockTime -> ClockTime -> TimeDiff<br>
diffClockTimes ct1 ct2 = ... -- Implementation-dependent<br>
<br>
toCalendarTime :: ClockTime -> IO CalendarTime<br>
toCalendarTime ct = ... -- Implementation-dependent<br>
<br>
toUTCTime :: ClockTime -> CalendarTime<br>
toUTCTime ct = ... -- Implementation-dependent<br>
<br>
toClockTime :: CalendarTime -> ClockTime<br>
toClockTime cal = ... -- Implementation-dependent<br>
<br>
calendarTimeToString :: CalendarTime -> String<br>
calendarTimeToString = formatCalendarTime defaultTimeLocale "%c"<br>
<br>
formatCalendarTime :: TimeLocale -> String -> CalendarTime -> String<br>
formatCalendarTime l fmt ct@(CalendarTime year mon day hour min sec sdec <br>
wday yday tzname _ _) =<br>
doFmt fmt<br>
where doFmt ('%':c:cs) = decode c ++ doFmt cs<br>
doFmt (c:cs) = c : doFmt cs<br>
doFmt "" = ""<br>
<br>
to12 :: Int -> Int<br>
to12 h = let h' = h `mod` 12 in if h' == 0 then 12 else h'<br>
<br>
decode 'A' = fst (wDays l !! fromEnum wday)<br>
decode 'a' = snd (wDays l !! fromEnum wday)<br>
decode 'B' = fst (months l !! fromEnum mon)<br>
decode 'b' = snd (months l !! fromEnum mon)<br>
decode 'h' = snd (months l !! fromEnum mon)<br>
decode 'C' = show2 (year `quot` 100)<br>
decode 'c' = doFmt (dateTimeFmt l)<br>
decode 'D' = doFmt "%m/%d/%y"<br>
decode 'd' = show2 day<br>
decode 'e' = show2' day<br>
decode 'H' = show2 hour<br>
decode 'I' = show2 (to12 hour)<br>
decode 'j' = show3 yday<br>
decode 'k' = show2' hour<br>
decode 'l' = show2' (to12 hour)<br>
decode 'M' = show2 min<br>
decode 'm' = show2 (fromEnum mon+1)<br>
decode 'n' = "\n"<br>
decode 'p' = (if hour < 12 then fst else snd) (amPm l)<br>
decode 'R' = doFmt "%H:%M"<br>
decode 'r' = doFmt (time12Fmt l)<br>
decode 'T' = doFmt "%H:%M:%S"<br>
decode 't' = "\t"<br>
decode 'S' = show2 sec<br>
decode 's' = ... -- Implementation-dependent<br>
decode 'U' = show2 ((yday + 7 - fromEnum wday) `div` 7)<br>
decode 'u' = show (let n = fromEnum wday in <br>
if n == 0 then 7 else n)<br>
decode 'V' = <br>
let (week, days) = <br>
(yday + 7 - if fromEnum wday > 0 then <br>
fromEnum wday - 1 else 6) `divMod` 7<br>
in show2 (if days >= 4 then<br>
week+1 <br>
else if week == 0 then 53 else week)<br>
<br>
decode 'W' = <br>
show2 ((yday + 7 - if fromEnum wday > 0 then <br>
fromEnum wday - 1 else 6) `div` 7)<br>
decode 'w' = show (fromEnum wday)<br>
decode 'X' = doFmt (timeFmt l)<br>
decode 'x' = doFmt (dateFmt l)<br>
decode 'Y' = show year<br>
decode 'y' = show2 (year `rem` 100)<br>
decode 'Z' = tzname<br>
decode '%' = "%"<br>
decode c = [c]<br>
<br>
show2, show2', show3 :: Int -> String<br>
show2 x = [intToDigit (x `quot` 10), intToDigit (x `rem` 10)]<br>
<br>
show2' x = if x < 10 then [ ' ', intToDigit x] else show2 x<br>
<br>
show3 x = intToDigit (x `quot` 100) : show2 (x `rem` 100)<br>
<br>
<p>
<body bgcolor="#ffffff"> <i>The Haskell 98 Library Report</i><br> <a href="index.html">top</a> | <a href="system.html">back</a> | <a href="locale.html">next</a> | <a href="libindex.html">contents</a> <br><hr>
</tt>
|
