Difference between revisions of "Cookbook/Dates And Time"

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== CPU time ==
 
== CPU time ==
Use [http://www.haskell.org/ghc/docs/latest/html/libraries/base/System-CPUTime.html#v%3AgetCPUTime System.CPUTime.getCPUTime] to get the CPU time in picoseconds.
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Use [http://www.haskell.org/ghc/docs/latest/html/libraries/base-4.12.0.0/System-CPUTime.html#v%3AgetCPUTime System.CPUTime.getCPUTime] to get the CPU time in picoseconds.
   
 
You can time a computation like this
 
You can time a computation like this

Latest revision as of 21:06, 6 January 2019

Finding today's date

import Data.Time

c <- getCurrentTime                  --> 2009-04-21 14:25:29.5585588 UTC 
(y,m,d) = toGregorian $ utctDay c    --> (2009,4,21)

Adding to or subtracting from a date

Problem Solution Examples
adding days to a date addDays
import Data.Time
a = fromGregorian 2009 12 31    --> 2009-12-31
b = addDays 1 a                 --> 2010-01-01
subtracting days from a date addDays
import Data.Time
a = fromGregorian 2009 12 31    --> 2009-12-31
b = addDays (-7) a              --> 2009-12-24

Difference of two dates

Problem Solution Examples
calculating the difference of two dates diffDays
import Data.Time
a = fromGregorian 2009 12 31    --> 2009-12-31
b = fromGregorian 2010 12 31    --> 2010-12-31
diffDays b a                    --> 365

CPU time

Use System.CPUTime.getCPUTime to get the CPU time in picoseconds.

You can time a computation like this

getCPUTimeDouble :: IO Double
getCPUTimeDouble = do t <- System.CPUTime.getCPUTime; return ((fromInteger t) * 1e-12)

main = do
    t1 <- getCPUTimeDouble
    print (fib 30)
    t2 <- getCPUTimeDouble
    print (t2-t1)