Re: [Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
Hello,
> the final RNG state from the first execution of your code and passing it as
> the initial > state to the second
original intention of my question: How can I change the runOneRandom
function (with RNG updates) to return [ThingK True...] samples instead
of Int?
My solution so far:
> import Random
> import Control.Monad
> import qualified Control.Monad.State as S
> import Test.QuickCheck.Gen
> import Test.QuickCheck.Arbitrary
Each thing can have one of three types:
> data Ontology = Thing1 Bool
> | ThingK Bool
> deriving (Show, Eq)
> instance Arbitrary Ontology where
>arbitrary =
>oneof [ return $ Thing1 True
> , return $ ThingK True
> , return $ Thing1 False
> , return $ ThingK False ]
Liked to have a state monad runner for my arbitrary things as in "Real World
Haskell", "Chapter 14. Monads" ("Random values in the state monad").
[RWH]:
> -- file: ch14/Random.hs
> type RandomState a = S.State StdGen a
[RWH]:
> -- file: ch14/Random.hs
> getRandom :: Random a => RandomState a
> getRandom =
> S.get >>= \gen ->
> let (val, gen') = random gen in
> S.put gen' >>
> return val
[RWH]:
> getOneRandom :: Random a => RandomState a
> getOneRandom = getRandom
[RWH]:
< runOneRandom :: IO Int
< runOneRandom = do
< oldState <- getStdGen
< let (result, newState) = S.runState getOneRandom oldState
< setStdGen newState
< return result
Updated RNG is used. TODO How to sort out empty lists.
> runOneRandom2 :: IO [Ontology]
> runOneRandom2 = do
> oldState <- getStdGen
> let (result, newState) = S.runState (getOneRandom :: RandomState Int)
> oldState
> setStdGen newState
> let result2 = unGen arbitrary newState 12 :: [Ontology]
> return result2
To compare the behaviour: But the Random Number Generator isn't
updated... I liked to have different [Ontology] occasions per call:
> genArray :: [Ontology]
> genArray = unGen arbitrary (mkStdGen 42) 12 :: [Ontology]
On more question remains though: Is there a more haskellish way of
doing this, especially having behaviour more like the arbitrary
function with no empty samples allowed?
Cheers
Daniel
2011/4/26 Daniel Kahlenberg :
> Oh thanks,
>
> hold on I'd like to have the genArray call generating distinctive
> results in one IO execution (meaning when
> I load the .lhs file in ghci):
>
> Prelude> genArray
> [ThingK True,Thing1 False]
>
> and when calling immediately again e. g.
>
> Prelude> genArray
> [Thing1 True]
>
> By now I only get one and the same again, i. e.:
>
> Prelude> genArray
> [ThingK True]
>
> Prelude> genArray
> [ThingK True]
>
> ...
>
> so I thought an adaptation of the `runTwoRandoms` approach as described
> in the RWH book could help.
>
> In other words the genArray should have similar behaviour as e. g. a
> `runOneRandom` function defined like:
>
>> getOneRandom :: Random a => RandomState a
>> getOneRandom = getRandom
>
>> runOneRandom :: IO Int
>> runOneRandom = do
>> oldState <- getStdGen
>> let (result, newState) = S.runState getOneRandom oldState
>> setStdGen newState
>> return result
>
> ... the rest of the code as in my first post...
>
> Testing it, different numbers expected as the RNG is updated each call:
>
> Prelude> runOneRandom
> 2033303743
>
> Prelude> runOneRandom
> -566930973
>
> ...
>
> Cheers
> Daniel
>
> 2011/4/26 Bryan O'Sullivan :
>> On Tue, Apr 26, 2011 at 3:04 AM, Daniel Kahlenberg
>> wrote:
>>>
>>> Thought getRandom function would be the best place to inject my unGen
>>> function
>>> call, but cannot get it to type-check:
>>
>> You haven't described what it is you're actually trying to do, and I'm
>> afraid your code doesn't help to understand that.
>
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
On Tue, Apr 26, 2011 at 9:16 AM, Daniel Kahlenberg wrote: > > hold on I'd like to have the genArray call generating distinctive > results in one IO execution The problem you're seeing is due to the fact that you're not taking the final RNG state from the first execution of your code and passing it as the initial state to the second. Since you're initialising each one with the same RNG state, you're getting the same results in each case. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
Oh thanks, hold on I'd like to have the genArray call generating distinctive results in one IO execution (meaning when I load the .lhs file in ghci): Prelude> genArray [ThingK True,Thing1 False] and when calling immediately again e. g. Prelude> genArray [Thing1 True] By now I only get one and the same again, i. e.: Prelude> genArray [ThingK True] Prelude> genArray [ThingK True] ... so I thought an adaptation of the `runTwoRandoms` approach as described in the RWH book could help. In other words the genArray should have similar behaviour as e. g. a `runOneRandom` function defined like: > getOneRandom :: Random a => RandomState a > getOneRandom = getRandom > runOneRandom :: IO Int > runOneRandom = do > oldState <- getStdGen > let (result, newState) = S.runState getOneRandom oldState > setStdGen newState > return result ... the rest of the code as in my first post... Testing it, different numbers expected as the RNG is updated each call: Prelude> runOneRandom 2033303743 Prelude> runOneRandom -566930973 ... Cheers Daniel 2011/4/26 Bryan O'Sullivan : > On Tue, Apr 26, 2011 at 3:04 AM, Daniel Kahlenberg > wrote: >> >> Thought getRandom function would be the best place to inject my unGen >> function >> call, but cannot get it to type-check: > > You haven't described what it is you're actually trying to do, and I'm > afraid your code doesn't help to understand that. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
On Tue, Apr 26, 2011 at 3:04 AM, Daniel Kahlenberg < d.kahlenb...@googlemail.com> wrote: > Thought getRandom function would be the best place to inject my unGen > function > call, but cannot get it to type-check: > You haven't described what it is you're actually trying to do, and I'm afraid your code doesn't help to understand that. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
Maybe this is a beginners question... But here my problems description:
> import Random
> import Control.Monad
> import qualified Control.Monad.State as S
> import Test.QuickCheck.Gen
> import Test.QuickCheck.Arbitrary
Each thing can have one of three types:
> data Ontology = Thing1 Bool
> | ThingK Bool
> deriving (Show, Eq)
> instance Arbitrary Ontology where
>arbitrary =
>oneof [ return $ Thing1 True
> , return $ ThingK True
> , return $ Thing1 False
> , return $ ThingK False ]
Liked to have a state monad runner for my arbitrary things as in "Real World
Haskell", "Chapter 14. Monads" ("Random values in the state monad").
[RWH]:
> -- file: ch14/Random.hs
> type RandomState a = S.State StdGen a
[RWH]:
< -- file: ch14/Random.hs
< getRandom :: Random a => RandomState a
< getRandom =
< S.get >>= \gen ->
< let (val, gen') = random gen in
< S.put gen' >>
< return val
[RWH]:
< -- file: ch14/Random.hs
< getTwoRandoms :: Random a => RandomState (a, a)
< getTwoRandoms = liftM2 (,) getRandom getRandom
[RWH]:
< -- file: ch14/Random.hs
< runTwoRandoms :: IO (Int, Int)
< runTwoRandoms = do
< oldState <- getStdGen
< let (result, newState) = S.runState getTwoRandoms oldState
< setStdGen newState
< return result
Thought getRandom function would be the best place to inject my unGen function
call, but cannot get it to type-check:
> getRandom :: Random a => RandomState [a]
> getRandom =
> S.get >>= \gen ->
> let (val, gen') = liftM2 (,) (unGen arbitrary gen 12) (random gen) in
> S.put gen' >>
> return val
A function not almost fulfilling my needs but the Random Number Generator isn't
updated... I liked to have different [Ontology] occasions per call:
> genArray :: [Ontology]
> genArray = unGen arbitrary (mkStdGen 42) 12 :: [Ontology]
Does anyone have the patience to help me out at least one step further?
Cheers
Daniel
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
