Difference between revisions of "Cookbook/Dates And Time"
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m (→Difference of two dates: typo) |
m (Fixed broken link) |
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| (One intermediate revision by one other user not shown) | |||
| Line 19: | Line 19: | ||
| [http://hackage.haskell.org/packages/archive/time/latest/doc/html/Data-Time-Calendar.html#v%3AaddDays addDays] |
| [http://hackage.haskell.org/packages/archive/time/latest/doc/html/Data-Time-Calendar.html#v%3AaddDays addDays] |
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|<haskell> |
|<haskell> |
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| − | import |
+ | import Data.Time |
a = fromGregorian 2009 12 31 --> 2009-12-31 |
a = fromGregorian 2009 12 31 --> 2009-12-31 |
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b = addDays 1 a --> 2010-01-01 |
b = addDays 1 a --> 2010-01-01 |
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| Line 27: | Line 27: | ||
| [http://hackage.haskell.org/packages/archive/time/latest/doc/html/Data-Time-Calendar.html#v%3AaddDays addDays] |
| [http://hackage.haskell.org/packages/archive/time/latest/doc/html/Data-Time-Calendar.html#v%3AaddDays addDays] |
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|<haskell> |
|<haskell> |
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| − | import |
+ | import Data.Time |
a = fromGregorian 2009 12 31 --> 2009-12-31 |
a = fromGregorian 2009 12 31 --> 2009-12-31 |
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b = addDays (-7) a --> 2009-12-24 |
b = addDays (-7) a --> 2009-12-24 |
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| Line 44: | Line 44: | ||
| [http://hackage.haskell.org/packages/archive/time/latest/doc/html/Data-Time-Calendar.html#v%3AdiffDays diffDays] |
| [http://hackage.haskell.org/packages/archive/time/latest/doc/html/Data-Time-Calendar.html#v%3AdiffDays diffDays] |
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|<haskell> |
|<haskell> |
||
| − | import |
+ | import Data.Time |
a = fromGregorian 2009 12 31 --> 2009-12-31 |
a = fromGregorian 2009 12 31 --> 2009-12-31 |
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b = fromGregorian 2010 12 31 --> 2010-12-31 |
b = fromGregorian 2010 12 31 --> 2010-12-31 |
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| Line 52: | Line 52: | ||
== CPU time == |
== CPU time == |
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| − | 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. |
+ | 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 |
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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)