Hallo!
I'd like to build a database model with winHugs that allows
a recursive relation. For example a single instance of
entity components is related with at least another row of
the entity components (1 to many relationship). How can I
do that?
Thank you for your attention!
For Bimap is there anything like Data.Map.insertWithKey ?
Stuart Cook wrote:
On Sat, Feb 9, 2008 at 7:36 AM, Dan Weston [EMAIL PROTECTED] wrote:
If order is important, the new bijective Data.Bimap class
http://code.haskell.org/~scook0/haddock/bimap/Data-Bimap.html
may be your best bet (I
On Sun, Feb 10, 2008 at 12:19 AM, ChrisK [EMAIL PROTECTED] wrote:
For Bimap is there anything like Data.Map.insertWithKey ?
No. I wanted to implement the insertWith family, but it wasn't clear
to me what should happen if the value produced by the user's function
already exists, bound to
Matthew Naylor wrote:
[snip]
Finally, when I say observable sharing, I don't necessarily mean it
as defined by Koen Claessen and David Sands. I simply mean the use of
unsafePerformIO to detect sharing, whether or not this is done by an
eq predicate on Refs. (I say this because I think there
On Feb 9, 2008 12:34 PM, Bertram Felgenhauer
[EMAIL PROTECTED] wrote:
ghc actually provides a primop for this:
reallyUnsafePtrEquality# :: a - a - Int#
Use at your own risk.
Why is it more than unsafe? 'unsafePerformIO' seems to me a lot
unsafer than 'reallyUnsafePtrEquality#'.
Also, is
Matthew Naylor wrote:
(snip)
Now, there remains the concern that Haskell's semantics does not
enforce sharing. A Haskell compiler is free to change the sharing a
program at a whim, unknowingly to the programmer who may be relying on
it in for an efficient program. However, to my knowledge,
On Thu, 7 Feb 2008, Albert Y. C. Lai wrote:
Is it good or bad to add:
instance (MonadIO m) = MonadIO (ParsecT s u m)
I don't see any reason not to add it - it's not as if we can prevent
people lifting to IO! Good catch.
--
[EMAIL PROTECTED]
A problem that's all in your head is still a
Am Freitag, 8. Februar 2008 17:14 schrieb Stefan Monnier:
You seem to write 12 as 1 :+ 2 instead of () :+ 1 :+ 2. But I think,
the latter representation should probably be prefered. With it, :+
always has a number as its left argument and a digit as its right.
Without the () :+ we
On Jan 25, 2008 11:40 AM, Simon Peyton-Jones [EMAIL PROTECTED] wrote:
Would you be interested in working at Microsoft Research for three months?
If so, you might want to think about applying for an internship.
Simon and I are looking for interns, starting in summer 2008. Lots of
Dave Bayer wrote:
What is the best way to embed an arbitrary file in a Haskell program?
I don't know the best way. I'd probably use FFI.
main.hs:
{-# LANGUAGE ForeignFunctionInterface #-}
module Main where
import Foreign
import Foreign.ForeignPtr
import qualified Data.ByteString as
On Feb 7, 2008 4:58 AM, David Menendez [EMAIL PROTECTED] wrote:
If you're doing any kind of backtracking or non-determinism, you might
consider the msplit operation defined in Backtracking, Interleaving,
and Terminating Monad Transformers
http://okmij.org/ftp/Computation/monads.html#LogicT.
On Feb 9, 2008, at 8:03 AM, Bertram Felgenhauer wrote:
Dave Bayer wrote:
What is the best way to embed an arbitrary file in a Haskell program?
I don't know the best way. I'd probably use FFI.
snip
The idea is then to use some existing tool that embeds binary
data in C programs.
Since
Consider the function
cond x y z = if x then y else z
I guess we can certainly say cond is strict in x.
But what about y and z?
If x is true, then cond is strict in y
If x is false, then cond is strict in z
So we can't really say cond is lazy nor strict in its second or third argument.
Am Samstag, 9. Februar 2008 17:33 schrieb Peter Verswyvelen:
Consider the function
cond x y z = if x then y else z
I guess we can certainly say cond is strict in x.
But what about y and z?
If x is true, then cond is strict in y
If x is false, then cond is strict in z
So we can't
Hi Tom,
In addition to the sharing problem, another shortcoming of Haskell
DSLs is they can not fully exploit the benefits of algebraic
datatypes. Specifically, pattern matching ADTs can only be used to
control the compile-time configuration of the target, it can't be used
to describe the
On Fri, 8 Feb 2008, Tom Hawkins wrote:
5) Forget embedding the DSL, and write a direct compiler.
In addition to the sharing problem, another shortcoming of Haskell
DSLs is they can not fully exploit the benefits of algebraic
datatypes. Specifically, pattern matching ADTs can only be used
On Fri, 8 Feb 2008, Wolfgang Jeltsch wrote:
Am Donnerstag, 7. Februar 2008 16:31 schrieben Sie:
Even if () would be preferred from the programmers point of view (I'm
not sure how much we could reduce the number of instances though), it
makes the representation less attractive on the
On Feb 9, 2008 11:33 PM, Alfonso Acosta [EMAIL PROTECTED] wrote:
On Feb 8, 2008 4:10 PM, Wolfgang Jeltsch [EMAIL PROTECTED] wrote:
example really applies here. Besides, you should be regarded :* as (,)
and not as a constructor which would take a number and a digit
Sorry for my lousy English,
On Feb 9, 2008 4:08 PM, Wolfgang Jeltsch [EMAIL PROTECTED] wrote:
So what would (D1 :* D1) :* (D2 :* D2) mean then?
Nothing. That value doesn't satisfy the Nat or Post class constraints
and should be taken into consideration.
Why should :* be provided a meaning? it is an unavoidable syntactical
On Feb 8, 2008 5:14 PM, Stefan Monnier [EMAIL PROTECTED] wrote:
How 'bout treating :+ as similar to `append' rather than similar to `cons'?
Basically treat :+ as taking 2 numbers (rather than a number and
a digit).
Interpreting it like that would certainly make make more sense. But
again, I
On Feb 8, 2008 4:10 PM, Wolfgang Jeltsch [EMAIL PROTECTED] wrote:
Am Donnerstag, 7. Februar 2008 16:31 schrieben Sie:
Even if () would be preferred from the programmers point of view (I'm
not sure how much we could reduce the number of instances though), it
makes the representation less
On Feb 9, 2008 12:28 AM, Tom Hawkins [EMAIL PROTECTED] wrote:
5) Forget embedding the DSL, and write a direct compiler.
In addition to the sharing problem, another shortcoming of Haskell
DSLs is they can not fully exploit the benefits of algebraic
datatypes. Specifically, pattern matching
On Fri, 8 Feb 2008, Matthew Naylor wrote:
Now recall that referential transparency lets you replace equals with
equals without changing the *value produced* by a program. Note that
it says nothing about preserving *runtime behaviour*. Sharing, for
example, may be lost. So if you do
On Fri, 8 Feb 2008, [EMAIL PROTECTED] wrote:
Hallo!
Let's suppose I have a list [a,b,c,d,c,d]. I'd like to write
a function that returns a new list without duplicates (in
the example [a,b,c,d]). How can I do that? What is the most
general way? I'd like to use the same function for a list
Hello to everybody
I am an new user of Haskel and generally in functional programming and I could
say that I am very impressed from this Language. Though I can't understand the
use of datatypes.
Let's take a firly simple situtation
e.g. data Pair a b = Pair a b
i.e. an new type with name Pair
On Feb 9, 2008, at 19:09 , Mattes Simeon wrote:
e.g. data Pair a b = Pair a b
struct Pair { a pair_a; b pair_b; };
data Either a b = Left a | Right b
union Either { enum { Left, Right } _tag; a either_left; b
either_right; };
(except that Haskell makes sure you use it properly, while C
On Fri, 8 Feb 2008, Brandon S. Allbery KF8NH wrote:
On Feb 8, 2008, at 11:14 , Stefan Monnier wrote:
You seem to write 12 as 1 :+ 2 instead of () :+ 1 :+ 2. But I
think, the
latter representation should probably be prefered.
(...)
How 'bout treating :+ as similar to `append' rather
On Feb 10, 2008 12:09 AM, Mattes Simeon [EMAIL PROTECTED] wrote:
Hello to everybody
I am an new user of Haskel and generally in functional programming and I
could
say that I am very impressed from this Language. Though I can't understand
the
use of datatypes.
Let's take a firly simple
A new experimental package, Finance-Treasury, has been uploaded to
hackage. It automates the fetching of Treasury's daily yield curve
data (XML) and translates the data into Data.Map representation. The
collection of historical data can go back to 1992.
Moving on to the implementation of fixed-sized vectors themselves ...
I have been trying to implement them as a GADT but I have run into
quite few problems. As a result, I'm considering to implement them
using the more-traditional phantom type-parameter approach. Anyhow,
I'd like to share those
Hi Matt,
On Feb 9, 2008 1:07 PM, Matthew Naylor [EMAIL PROTECTED] wrote:
If you go the real compiler route, would it not make sense to take the
DSL as the source language rather than Haskell? Or are the DSL and
Haskell quite similar?
The two are nearly identical. In fact the only
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