Greg Buchholz wrote:
> I'm wondering about creating a data structure that has the type of
> decreasing numbers.
> I can try...
>
> class Pre a b | a -> b
> instance Pre (Succ a) a
> instance Pre Zero Zero
>
> data (Pre a b) => Seq a = Cons a (Seq b) | Nil
>
> decreasing = Cons three (Cons two
Greg,
What about the following (tested with GHC 6.6)?
{-# OPTIONS -fglasgow-exts #-}
data Zero = Zero
data Succ n = Succ n
zero = Zero
one = Succ zero
two = Succ one
three = Succ two
-- etc
data Seq :: * -> * where
Nil :: Seq Zero
Cons :: Succ n -> Seq n -> S
This is the best introduction to "Monads" for newbies and imparative
mined that I'v ever read! For a long time I was searching for such an
excellent text on monads. Ofcourse there are many good text there. But
all of them are about mathematics and how clever the monads are. After
all most of them
Hello,
Good, writeCSV writes out every row immediately after it got it. I
eliminated (++ [nl]) in the hope of reducing the constant factor
slightly. Using difference lists for that is nicer but here you go.
I'm not sure how you'd use difference lists here.
Also, for some reason GHC runs sligh
Spencer Janssen wrote:
] Here's an attempt with GADTs:
]
] \begin{code}
] {-# OPTIONS_GHC -fglasgow-exts #-}
] data Succ a
] data Zero
] data Seq a b where
] Cons :: a -> Seq a b -> Seq a (Succ b)
] Nil :: Seq a Zero
] \end{code}
]
] Seems to work for me.
Hmm. Maybe I'm missing som
Here's an attempt with GADTs:
\begin{code}
{-# OPTIONS_GHC -fglasgow-exts #-}
data Succ a
data Zero
data Seq a b where
Cons :: a -> Seq a b -> Seq a (Succ b)
Nil :: Seq a Zero
\end{code}
Seems to work for me.
Spencer Janssen
On Oct 17, 2006, at 6:37 PM, Greg Buchholz wrote:
I'm
I'm wondering about creating a data structure that has the type of
decreasing numbers. If I want an increasing list, it is easy...
> {-# OPTIONS -fglasgow-exts #-}
>
> data Succ a = S a deriving Show
> data Zero = Z deriving Show
>
> data Seq' a = Cons' a (Seq' (Succ a)) | Nil' deri
I've been writing some code that relies heavily on the type system.
Some of my polymorphic functions end up too polymorphic.
I'm looking for some tips and references regarding prescribing
poly-/mono-morphism. I know of three ways to do it:
1) rely on the monomorphism-restriction -- kind of scary
Am Dienstag, 17. Oktober 2006 19:37 schrieb Víctor A. Rodríguez:
> > What's wrong with doing it this way?
> >
> > -- ** UNTESTED CODE **
> >
> > verifyAdd :: Int -> Int -> Int -> Bool
> > verifyAdd a b sum | a + b == sum = True
> > otherwise = False
> >
> > testAddMundane :: Int -> Int -> Bool
> >
On Oct 17, 2006, at 1:07 PM, Robert Dockins wrote:
On Oct 17, 2006, at 12:55 PM, Gregory Wright wrote:
Hi Rob,
I've built Edison 1.2.0.1 using ghc-6.6. (I'm testing the macports,
formerly darwinports, packages for the new 6.6 release.)
The build goes fine, but the ./Setup register fails
On Oct 17, 2006, at 1:37 PM, Víctor A. Rodríguez wrote:
What's wrong with doing it this way?
-- ** UNTESTED CODE **
verifyAdd :: Int -> Int -> Int -> Bool
verifyAdd a b sum | a + b == sum = True
otherwise = False
testAddMundane :: Int -> Int -> Bool
testAddMundane a b = verifyAdd a b (a + b)
> What's wrong with doing it this way?
>
> -- ** UNTESTED CODE **
>
> verifyAdd :: Int -> Int -> Int -> Bool
> verifyAdd a b sum | a + b == sum = True
> otherwise = False
>
> testAddMundane :: Int -> Int -> Bool
> testAddMundane a b = verifyAdd a b (a + b)
>
> -- all the IO-dependent stuff is below
On Oct 17, 2006, at 12:55 PM, Gregory Wright wrote:
Hi Rob,
I've built Edison 1.2.0.1 using ghc-6.6. (I'm testing the macports,
formerly darwinports, packages for the new 6.6 release.)
The build goes fine, but the ./Setup register fails claiming that
the directory
/opt/local/lib/EdisonAPI
Hi,
> What's wrong with doing it this way?
>
> -- ** UNTESTED CODE **
>
> verifyAdd :: Int -> Int -> Int -> Bool
> verifyAdd a b sum | a + b == sum = True
> otherwise= False
>
> testAddMundane :: Int -> Int -> Bool
> testAddMundane a b = verifyAdd a b (a + b)
>
> -- all the I
Hi Rob,
I've built Edison 1.2.0.1 using ghc-6.6. (I'm testing the macports,
formerly darwinports, packages for the new 6.6 release.)
The build goes fine, but the ./Setup register fails claiming that the
directory
/opt/local/lib/EdisonAPI-1.2/ghc-6.6/include does not exist. I can
make the
On Tue, Oct 17, 2006 at 01:21:38PM -0300, V?ctor A. Rodr?guez wrote:
> To: haskell-cafe@haskell.org
> From: "Víctor A. Rodríguez" <[EMAIL PROTECTED]>
> Date: Tue, 17 Oct 2006 13:21:38 -0300
> Subject: [Haskell-cafe] Newbie and working with IO Int and Int
>
> Hi all,
>
> I'm really newbie to Hask
On Oct 17, 2006, at 12:21 PM, Víctor A. Rodríguez wrote:
Hi all,
I'm really newbie to Haskell, and working on a program I'm trying
to make
some testing.
I make some test on certain know values ( e.g. adding 10 to 15 must
return
25) and some test on random values (eg. adding rnd1 to rnd2 m
Víctor A. Rodríguez wrote:
> Hi all,
>
> I'm really newbie to Haskell, and working on a program I'm trying to make
> some testing.
> I make some test on certain know values ( e.g. adding 10 to 15 must return
> 25) and some test on random values (eg. adding rnd1 to rnd2 must return
> rnd1+rnd2).
>
Hi all,
I'm really newbie to Haskell, and working on a program I'm trying to make
some testing.
I make some test on certain know values ( e.g. adding 10 to 15 must return
25) and some test on random values (eg. adding rnd1 to rnd2 must return
rnd1+rnd2).
The problem that makes me mad is the rando
> I installed HDBC, but when I tried running a simple program that used
> it, I get the error message
>
> ghc-6.6:
> /usr/local/lib/HDBC-postgresql-1.0.1.0/ghc-6.6/HSHDBC-postgresql-1.0.1.0.o:
> unknown symbol `PQserverVersion'
Ah, I figured it out. The PQserverVersion function is documented in
Nils Anders Danielsson <[EMAIL PROTECTED]> writes:
> On Mon, 16 Oct 2006, Jón Fairbairn <[EMAIL PROTECTED]> wrote:
>
> > I made a more concrete proposal later and Phil Wadler tidied it up.
> > I think It even got as far as a draft of the language, [...]
>
> Do you know where this proposal/draft
jeff p wrote:
> Hello,
>
>> Yet, I'm a bit astonished. I thought that when compiling with -O2,
>> cosmetic changes should become negligible. Perhaps the strict foldl' has
>> an effect?
>>
> Perhaps... but I doubt that is the main reason. At the moment I have
> no idea why there is such a discrepan
On Mon, 16 Oct 2006, Jón Fairbairn <[EMAIL PROTECTED]> wrote:
> I made a more concrete proposal later and Phil Wadler tidied it up.
> I think It even got as far as a draft of the language, [...]
Do you know where this proposal/draft can be found?
--
/NAD
___
> I think that you misunderstood what I said. When we went from FRP to Yampa,
> we
> changed from using signals directly, i.e. Signal a, to using signal
> functions, i.e.:
>
> SF a b = Signal a -> Signal b
>
> When we did this, we made SF abstract, and we adopted the arrow framework to
>
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