Is there some abstraction in current ghc library
that implements something like Reader, but where
the value of the environment is updated at every
"step"?
do-it-yourself? you can start from reader definition and add what you
need. you just need to make "initial state" consisting from state
itsel
Is there some abstraction in current ghc library that implements
something like Reader, but where the value of the environment is
updated at every "step"?
>>>
> It doesn't quite make sense, because one "step" isn't well defined.
> How many "steps" is "return (f x)" ? how
Mauricio <[EMAIL PROTECTED]> wrote:
> [...]
>
Are you sure you don't want to use monad transformers?
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Are you sure you don't want to use monad transformers?
No. Do you have a sugestion on how could I do
it in this situation?
Maurício
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> Hi Mauricio. What you want actually already exists in QuickCheck as
> the "Gen" monad.
>
> newtype Gen a
> = Gen (Int -> StdGen -> a)
>
> instance Monad Gen where
> return a= Gen (\n r -> a)
> Gen m >>= k =
> Gen (\n r0 -> let (r1,r2) = split r0
> Gen m' = k
Maurcio <[EMAIL PROTECTED]> wrote:
> >
> >> [...]
> >>
> > Are you sure you don't want to use monad transformers?
> >
>
> No. Do you have a sugestion on how could I do
> it in this situation?
>
Not really, mainly because if monad transformers don't confuse you you
should double-check if yo
Hello Mauricio,
Thursday, November 6, 2008, 2:52:16 PM, you wrote:
> that. But I wanted to know if there's already the
> "right way to do it" instead of my "newbie way to
> do it" :)
"All about monads" doesn't mention it, at least :)
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Mauricio wrote:
Is there some abstraction in current ghc library
that implements something like Reader, but where
the value of the environment is updated at every
"step"?
do-it-yourself? you can start from reader definition and add what you
need. you just need to make "initial state" consisting
Mauricio wrote:
The problem is that I need 'a' or 'b' above to sometimes also change the
environment. I think with this method I could not get that.
I no longer understand what you want.
I thought you wanted an environment which automatically changed every
"step".
I showed you how you can
Hi Mauricio. What you want actually already exists in QuickCheck as
the "Gen" monad.
>From
>http://hackage.haskell.org/packages/archive/QuickCheck/1.1.0.0/doc/html/src/Test-QuickCheck.html#Gen
newtype Gen a
= Gen (Int -> StdGen -> a)
instance Monad Gen where
return a= Gen (\n r -> a)
On Fri, Nov 07, 2008 at 10:41:01AM +0100, Achim Schneider wrote:
>
> But then, you either want a ReaderT r State s or StateT s Reader r,
> depending on how you want to write your code... the main thing that
> confuses me right now is that nesting order doesn't seem to matter that
> much in this ca
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