s1.dlut.edu.cn/newVersion/Files/dsxx/610.pdf
But this library (and the corresponding article) may help me in the future.
Thanks,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
olynomial of second degree to be used at runtime.
We would put some placeholders in the code where the result of the pre-
processing calculation would enter.
Thanks in advance,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell
condensed and easy to remember
notation; still better if it is easily extended to higher dimensions/orders
(unfortunately, generally these notations are not taught at university).
Regards,
TP
o...@okmij.org wrote:
> Well, I guess you might be interested in geometric algebra then
>
:
j = 3
and then define in another module:
---
h x = $([|j|])
main = do
print $ h undefined
---
I obtain "3" as expected.
However, I do not achieve to make this system work with an infix
declaration:
infix $([| j |]) +
I obtain:
parse error on inpu
TP wrote:
> 2/ If I define in a module:
>
> j = 3
>
> and then define in another module:
>
> ---
> h x = $([|j|])
> main = do
> print $ h undefined
> ---
>
> I obtain "3" as expected.
>
> However,
Base n ++ " = " )) ++ show $(varE n) ) |]
by
pr n = [| putStrLn ( $([| (nameBase n) ++ " = " |]) ++ show $(varE n) ) |]
I again get the error
"""
No instance for (Lift Name) arising from a use of `n'
Possible fix: add an instance declaratio
parser needs a way to generate an AST
> representation, which is what Lift is for.
Ok, I think I understand that (we need some method to transform a value at
data level in a token of an AST), but it seems to me it does not answer my
question above. But I am probably wrong.
Thanks
TP
above in Haskell works in
MetaOCaml).
What is strange is that:
* in the version using "lift", the definition of lift asks for the output of
(nameBase n) to be an instance of Lift, what is the case because it is a
string (cf my previous post in this thread).
* whereas in the s
guage.Haskell.TH.Syntax
p :: Lift a => a -> ExpQ
p n = [| show n |]
it works correctly.
Why GHC is able to infer the typeclass constraint (Num a) in 1/, but not
(Lift a) in 2/?
Thanks in advance,
TP
___
Haskell-Cafe mailin
Adam Gundry wrote:
> If you leave off the type signature, as you did for sum', the
> right thing will be inferred.
Thanks Adam and Ivan. Very stupid question...
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.
am unable to list them. I think it is
important to have the reasons in mind. Could you help me?
Thanks in advance,
TP
PS: the complete Haskell example:
---
module MakeVard where
import Language.Haskell.TH
makeVard :: Monad m => String -> m [Dec]
-- Equiva
only be done by doE (or DoE) and
compE (or CompE) according to
http://www.haskell.org/ghc/docs/latest/html/libraries/template-haskell-2.8.0.0/Language-Haskell-TH.html#v:doE
But doE is not a solution as we have seen above, and compE is to construct
list comprehensions, which is a different thin
do with a let-statement; it requires something else
> following it. You have nothing following it, as shown by the above
> fragment from the error message.
Yes, I have explained why: to be able to see the evaluation of the splice;
otherwise I obtain "Not in sc
(IntegerL 1)))
> :i parseDecs
parseDecs ::
String -> Either String [Language.Haskell.TH.Syntax.Dec]
-- Defined in `Language.Haskell.Meta.Parse'
> :i parseExp
parseExp :: String -> Either String Language.Haskell.TH.Syntax.
tick to non-let expressions in the "main" part of a script,
when it comes to TH. It should nevertheless allow me to call functions, make
tests, etc.
Thanks,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
t get any error below.
$ ghci
> import Data.Ratio
> 2::Rational
2 % 1
Thanks in advance,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
ion (Tensor n) Scalar (Tensor n)
-- Defined at
test_overlapping_instance_with_typelevelinteger_test.hs:34:10
In the expression: s * s
In an equation for `a': a = s * s
In the expression:
do { let s = ...;
let a = s * s;
print a }
Thanks in ad
it does not look at the most specific instance
by examining the instance context? Is it OK, or is it a deficiency?
Thanks,
TP
-
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE
TP wrote:
> But I have still a question: is the behavior of GHC correct in the example
> of my initial post?
See here:
http://www.haskell.org/ghc/docs/7.6.3/html/users_guide/type-class-extensions.html#instance-overlap
"""
When matching, GHC takes no account of the co
ot;
So, what do I miss? Isn't the vocabulary different here?
And I do not understand what is written if I take your definition (which is
indeed the definition in the Haskell report).
Thanks in advance,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
e below?
2/ It seems there is no possibility to generate bytecode, contrary to OCaml.
Is it correct? Is there an alternative?
What is interesting with bytecode run with "ocamlrun" is that the process of
generating the bytecode is very fast, so it is very convenient to test the
program being w
gument of `(°)', namely `q'
In the expression: p ° q
Prelude>
What's the problem here? How can I obtain the type of p°q?
Thanks in advance,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
the correct way to do that?
I have tried:
---
instance Num ListOfInt where
l1 + l2 = ListOfInt $ getZipList $ (+) <$> ZipList (getList l1) <*>
ZipList (getList l2)
---
Isn't it too
Hi,
I don't known the advanced features and extensions of GHC at all.
Look at the following program:
f :: Integer -> Integer -> IO Integer
f a b = do
print $ "first argument=" ++ (show a)
print $ "second argument=" ++ (show b)
print $ a+b
return (a+b)
main = do
instance Show a => Show [a] -- Defined in GHC.Show
instance [overlap ok] Show [Foo]
-- Defined at test_overlappinginstances.hs:5:10-19
The overlap is ok ("overlap ok" does not appear if not using the prag
instances at:
http://book.realworldhaskell.org/read/using-typeclasses.html#id608052
but it does not seem to work well; or it is rather tricky: I have been unable
to make my initial post example work with overlapping instances. However, I
don't see why it could not work.
Thanks
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
have I to comment all the Show instances of
my code, and add "Show" in "deriving (...)" for each of my types? If this is
the only possibility, is there some script around here to do that
automatically?
Thanks in advance,
TP
___
Has
etty printing (not over several lines as in classical Computer
Algebra Sytems). Why not using my own Show implementation to do that?
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
Hi,
I am currently reading documentation on Generalized Algebraic Data Types:
http://en.wikibooks.org/wiki/Haskell/GADT
I have a question concerning this page. Let us consider the following code
proposed in the page:
--
-- Phantom type variable a (does not appea
) does not allow to know the type of a. It may be
of type Expr String as you have shown:
*Main> let expr = I 5 :: Expr String
*Main> expr
I 5
*Main> :t expr
expr :: Expr String
So we may have anything for «a» in «Expr a» input type of eval. These
multiplicity of values for «a» cannot matc
in "pseudo-language":
data Vector = TensorVar 1 String
Because a vector is a tensor of order 1.
Is this possible? I have tried type synonyms and newtypes without any success.
Thanks a lot,
TP
___
Haskell-Cafe mailing list
Haskell-C
ds to TensorVar with the integer equal to 1.
The idea is to avoid duplicating code, by reusing the tensor type and data
constructor. At some place in my code, in some definition (say, of a vector
product), I want vectors and not more general tensors.
TP
On Saturday, April 27, 2013 16:16:49 Yury Su
the following days, according to my
needs.
Thanks a lot,
TP
On Sunday, April 28, 2013 07:58:58 Stephen Tetley wrote:
> What you probably want are type level integers (naturals)
>
> Yury Sulsky used them in the message above - basically you can't use
> literal numbers 1,2,3,... et
s.
Thanks,
TP
On Monday, April 29, 2013 08:19:43 Richard Eisenberg wrote:
> There's a lot of recent work on GHC that might be helpful to you. Is it
> possible for your application to use GHC 7.6.x? If so, you could so
> something like this:
>
> {-# LANGUAGE DataKinds, GADTs
GHC stack-space overflow: current limit is 536870912 bytes.
Use the `-K' option to increase it.
Why (I imagine this is because there is an infinite loop in the construction
of the show function)? Is there any workaround?
Thanks,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
, father :: Person Gender } -> Person Gender
deriving instance Show (Person Gender)
main = do
let a = Alive "Joe" 60 Dead :: Person Male
let b = Alive "Jim" 70 a :: Person Male
print a
print b
How to modify it?
Thanks a l
data Gender = Male | Female
data Person :: Gender -> * where
Dead :: forall (a :: Gender). Person a
Alive :: { name :: String
, weight :: Float
, father :: forall (a :: Gender). Person a } -> forall (b ::
Gender). Person b
deriving instance Sho
ead :: Person a
> Alive :: { name :: String
> , weight :: Float
> , father :: Person b } -> Person a
>
> deriving instance Show (Person a)
Thanks so much, it is now perfectly clear. A lot of things learned with this
dummy example.
TP
___
Richard Eisenberg wrote:
> There's a lot of recent work on GHC that might be helpful to you. Is it
> possible for your application to use GHC 7.6.x? If so, you could so
> something like this:
>
> {-# LANGUAGE DataKinds, GADTs, KindSignatures #-}
>
> data Nat = Zero | Succ Nat
>
> type One = Suc
++ str ++ ” of order ”
++ (show (c2num order))
Thanks in advance,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
So, in the first case, c has a too restricted kind, and in the second one,
it has a too broad kind in the definition of cpred. I have tried several
things without any success.
How to compile that code?
Thanks,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
The reason is that the information that p1 and p2 are Male seems to be
"lost" when we construct the child "Child "Jack" p1 p2", probably because
GHC only sees that in the type signature of Child, we have a mo
ot;, "Child3" (imagining a world where every people has
three children). The problem is that I am compelled to repeat the context
"(PrettyPrint (Person a), PrettyPrint (Person b))" for each one of the
constructors. Is there any way to specify the context onl
Box (2::Float)
print $ a == b
print $ a == a
--
Is this the right way to go? Is there any other solution?
Thanks,
TP
___
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
ite a Typeable instance if you want one. The process is somewhat
trickier than you might expect, due to the fact that Typeable does
some unsafe stuff. But there are plenty of examples for how to do it
safely.
"""
Where are these examples that can
TP wrote:
> Where are these examples that can help me to write my instance?
> I have tried to read the source of the implemented instances in
> data.typeable, not so easy for me.
Ok, by doing a better search on Google ("instance typeable " blog), I have
found interesting
untime dimension checks, everything
is detected at compilation. So the choice of putting the order in the type
seems to be correct.
My only need to use Typeable comes from the heterogeneous list. But how to
do without?
Thanks,
TP
Richard Eisenberg wrote:
> Thankfully, the problem you have
prefer). So I have three instances for scalar product '⋅'. I don't see how
to combine this idea of overloading or derivation function with what you
proposed. But I have perhaps missed something.
Thanks,
TP
(*): That is to say the list of tensors of which one tensor depends, e.g.
g a)
main = do
let one = undefined :: Sing ('Succ 'Zero)
print one
---
The error is simply:
---
test_noinhabitant_corrected.hs: Void showsPrec
---
Why?
Thanks,
TP
References:
--
(1):
https://groups.google.com/fo
ial examples in part (1) of Post
Scriptum below. We have a concrete type Foo clearly of kind `*`, so bottom
(undefined in Haskell) is an inhabitant of Foo. Why should I be compelled to
add another inhabitant (a data constructor) to get bottom printed? Bottom
existence is independent from oth
> discovery of undefined in a running program. (GHC has implemented an
> exception that allows exception-handling code, written in the IO monad, to
> catch a use of undefined, but I would be highly suspicious of code that
> used this feature.)
Interesting, I will remember that.
T
with GHC 7.6.2, the message is
different because recent improvements in Typeable are not present (1).
What is the problem? I've tried different things without success.
Tell me if the "beginners" diffusion list is more suitable than Haskell-
Cafe.
Thanks,
TP
(1):
http://hauptwerk.bl
’
What is the problem?
Is it possible that it is a bug in GHC? Indeed, we had unwanted similar
error messages recently:
http://hackage.haskell.org/trac/ghc/ticket/7704
Thanks,
TP
PS: the complete program for a test that shows the error:
--
{-# LANGUAGE GADTs
'Zero
deriving instance Typeable 'Succ
data Box where
Box :: (Typeable s, Show s, Eq s) => s -> Box
deriving Typeable
data Proxy a = P deriving (Typeable, Show, Eq)
deriving instance Show Box
instance Eq Box where
(Box s1) == (Box s2) = Just s1 == cast s2
main = d
Nat (P (Succ n)) = SSucc (mkSNat (P n))
main = do
let one = undefined :: Proxy ('Succ 'Zero)
print one
print $ mkSNat (P one)
--
Thanks,
TP
References:
---
[1]: https://groups.google.com/forum/?fromgroups#!topic/haskell-c
ade `'Succ n` and `Zero`
instances of MkSNat; are we compelled to put a constraint because Haskell
makes the hypothesis that o could be another type of kind Nat different from
`'Succ n` and `Zero`? If yes, is it related to the sentence I have already
read: "Typeclasses are op
gnitude 10^4 lines),
it is necessary to have types (I would not use Haskell for a small script,
of course). I feel also, from my coding experience, that states are a real
problem in traditional C/C++/Python/... code, and I want to give a try with
Haskell, monads, perhaps arrows, reactive progra
57 matches
Mail list logo
