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Today's Topics:
1. Fwd: [Haskell-beginners] combinatorial (Patrick LeBoutillier)
2. Re: combinatorial (Michael Mossey)
3. Re: Important coding guideline and library proposal
(a...@spamcop.net)
4. FFI and Cabal (Jeffrey Drake)
5. Retrieving the decimal portion of a Double (Dominic Sim)
6. Re: Retrieving the decimal portion of a Double (Shawn Willden)
7. recommended way to get haskell 6.10 installed on ubuntu
hardy? (Joe Van Dyk)
8. Re: recommended way to get haskell 6.10 installed on ubuntu
hardy? (Tony Morris)
----------------------------------------------------------------------
Message: 1
Date: Sun, 22 Nov 2009 17:04:11 -0500
From: Patrick LeBoutillier <patrick.leboutill...@gmail.com>
Subject: Fwd: [Haskell-beginners] combinatorial
To: beginners <beginners@haskell.org>
Message-ID:
<b217a64f0911221404g118e9281t57e5222bd6c44...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Forgot to forward my response to the list...
---------- Forwarded message ----------
From: Patrick LeBoutillier <patrick.leboutill...@gmail.com>
Date: Sun, Nov 22, 2009 at 5:03 PM
Subject: Re: [Haskell-beginners] combinatorial
To: "Michael P. Mossey" <m...@alumni.caltech.edu>
Michael,
Here's how I would go about this:
type MidiPitch = Int
range :: [MidiPitch]
range = [10..90]
-- Just a dummy eval function, allows up or down one unit
eval ps | length ps <= 1 = Just 1.0
eval ps | length ps > 1 =
let a = last ps
b = last . init $ ps in
if abs (a - b) == 1
then Just 1.0
else Nothing
coolFunc :: Int -> MidiPitch -> ([MidiPitch] -> Maybe Float) -> [[MidiPitch]]
coolFunc n p f = generate n f [[p]]
-- Generate MidiPitch lists up to a given length, making sure each step
-- satisfies the eval function
generate :: Int -> ([MidiPitch] -> Maybe Float) -> [[MidiPitch]] ->
[[MidiPitch]]
generate n f cs | n == 1 = cs
generate n f cs = generate (n-1) f $ concat . map (\p -> try p cs) $ range
-- Tries to add a MidiPitch to each of the MidiPitch lists, keep
-- only the sequences that pass the eval.
try :: MidiPitch -> [[MidiPitch]] -> [[MidiPitch]]
try p = filter (not . null) . map (test p)
where test p ps =
let ps' = ps ++ [p] in
case eval ps' of
Nothing -> []
otherwise -> ps'
It's seems to work, although I'm sure many bits sould be made more elegant...
Note: After that another pass would be required over the result set to
find the sequences that have the highest scores.
Patrick
On Sun, Nov 22, 2009 at 5:25 AM, Michael P. Mossey
<m...@alumni.caltech.edu> wrote:
> I'm trying to write a combinatorial search algorithm with evaluation, and
> kind of stuck. Not sure how to do this.
>
> I'm constructing a musical phrase, which is a list of MidiPitch:
>
> [MidiPitch]
>
> I have an evaluation function that determines the fitness of any given
> phrase:
>
> eval :: [MidiPitch] -> Maybe Float
>
> This returns Nothing if the phrase is completely unacceptable.
>
> The idea is to build up a phrase one midi pitch at a time, choosing all
> possible next pitches (notes) from a range:
>
> next pitch comes from: [10..90]
>
> Most of the pitches will result in a phrase that evaluates to Nothing, so
> the combinatoral "explosion" will be limited.
>
> I'd like to write a function that constructs a phrase of length n, and in
> fact will have to return a list of all phrases that have equal scores of the
> maximum.
>
> -- <length of output phrase> -> <first pitch> -> <eval func> ->
> -- <all tied phrases of best score>
> coolFunc :: Int -> MidiPitch -> ([MidiPitch] -> Maybe Float) ->
> [[MidiPitch]]
>
> I am stuck on how to write this.
>
> thanks,
> Mike
>
>
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
>
--
=====================
Patrick LeBoutillier
Rosemère, Québec, Canada
--
=====================
Patrick LeBoutillier
Rosemère, Québec, Canada
------------------------------
Message: 2
Date: Sun, 22 Nov 2009 14:30:57 -0800
From: Michael Mossey <m...@alumni.caltech.edu>
Subject: Re: [Haskell-beginners] combinatorial
To: "Edward Z. Yang" <ezy...@mit.edu>
Cc: beginners <beginners@haskell.org>
Message-ID: <4b09bba1.2040...@alumni.caltech.edu>
Content-Type: text/plain; charset=UTF-8; format=flowed
Edward Z. Yang wrote:
> We can relax this requirement by returning a list of all phrases that
> are of length n (and were not unacceptable) and then doing some kind
> of fold.
Thanks for the advice and code.
> Note that since your evaluation function is not incremental
> (i.e. I can't pass it a partial evaluation) I don't maintain scores
> in workFunc.
I'm not totally exactly sure what you mean here, but my evaluation function
can in fact evaluate phrases of any length.
In fact, I realized after seeing your reply that I failed to describe my
problem well at all.
Here's what I had in mind for a search algorithm. The idea is to combine
features of greedy and broad search. I have no idea is this is a good idea.
It's just a thought.
Let's say we start by evaluating all lists of length 2 and picking those
tied for the maximum score. Then the algorithm is,
for each input list of length 2 tied for maximum,
make all lists of length 3 that are acceptable (that don't return
Nothing when evaluated)
concat all those
evaluate all of them and pick all tied for the maximum
feed into next step (continue with lengths 4..N.)
The idea is that's a greedy algorithm that still allows for some breadth of
search by looking at ties. In my scoring system there will often be ties.
Thanks,
Mike
------------------------------
Message: 3
Date: Sun, 22 Nov 2009 21:54:10 -0500
From: a...@spamcop.net
Subject: Re: [Haskell-beginners] Important coding guideline and
library proposal
To: beginners@haskell.org
Message-ID: <20091122215410.aqwbhyiog2sc44cc-...@webmail.spamcop.net>
Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";
format="flowed"
G'day all.
Quoting Daniel Fischer <daniel.is.fisc...@web.de>:
> Proposal:
> rename 'length' to
> 'yesIReallyWantToKnowTheExactLengthOfThisListSoPleaseCalculateItForMe'
> to reduce performance bugs caused by naive uses of length.
genericYesIReallyWantToKnowTheExactLengthOfThisListSoPleaseCalculateItForMe
Another option is to rename Data.List to Data.List.YesIKnowThisIsNotAnArray.
Cheers,
Andrew Bromage
------------------------------
Message: 4
Date: Mon, 23 Nov 2009 02:35:00 -0500
From: Jeffrey Drake <iae...@me.com>
Subject: [Haskell-beginners] FFI and Cabal
To: "beginners@haskell.org Beginners Haskell" <beginners@haskell.org>
Message-ID: <91887885400682927252573119286481217153-webm...@me.com>
Content-Type: text/plain; charset=ISO-8859-1
I am trying to use FFI to access some windows console functions via two simple
C functions I created.
Essentially my module looks like is this:
{-# CFILES mouse.c #-}
{-# LANGUAGE ForeignFunctionInterface #-}
module Mouse where
-- import Foreign
import Foreign.C.Types
foreign import ccall unsafe "mouse.h SetupConsole" c_setupConsole :: IO CInt
foreign import ccall unsafe "mouse.h MouseEvent" c_mouseEvent :: IO CInt
setupConsole :: IO Bool
setupConsole = do c <- c_setupConsole
return $ if c == 0
then True
else False
mouseEvent :: IO (Maybe (Int, Int))
mouseEvent = do c <- c_mouseEvent
let d = toInteger c
let e = (fromInteger d)::Int
return $ if e < 0
then Nothing
else Just (e `mod` 256, e `div` 256)
It seems to compile fine. The problem comes when I need to link.
Linking dist\build\BoardGames\BoardGames.exe ...
dist\build\BoardGames\BoardGames-tmp\Mouse.o:fake:(.text+0x15): undefined
reference to `SetupConsole'
dist\build\BoardGames\BoardGames-tmp\Mouse.o:fake:(.text+0x11d): undefined
reference to `MouseEvent'
collect2: ld returned 1 exit status
The problem seems obvious - it isn't compiling OR linking mouse.c which is this:
#include <windows.h>
int SetupConsole()
{
HANDLE hStdin;
DWORD fdwMode, fdwSaveOldMode;
int counter=0;
hStdin = GetStdHandle(((DWORD)-10));
if (hStdin == ((HANDLE)(LONG_PTR)-1))
return -3;
if (! GetConsoleMode(hStdin, &fdwSaveOldMode) )
return -2;
fdwMode = 0x0010;
if (! SetConsoleMode(hStdin, fdwMode) )
return -1;
return 0;
}
int MouseEvent()
{
HANDLE hStdin;
INPUT_RECORD irInBuf[128];
short x, y;
unsigned i;
DWORD cNumRead;
static int ignoreNext = 0;
hStdin = GetStdHandle(((DWORD)-10));
if (hStdin == ((HANDLE)(LONG_PTR)-1))
return -2;
if (!ReadConsoleInputW(
hStdin,
irInBuf,
128,
&cNumRead) )
return -1;
for (i = 0; i < cNumRead; i++)
{
if (irInBuf[i].EventType == 0x0002 &&
irInBuf[i].Event.MouseEvent.dwEventFlags == 0)
{
if (ignoreNext == 1)
{
ignoreNext = 0;
return -1;
}
x =
irInBuf[i].Event.MouseEvent.dwMousePosition.X;
y =
irInBuf[i].Event.MouseEvent.dwMousePosition.Y;
ignoreNext = 1;
return x + (y << 8);
}
else
{
continue;
}
}
return -1;
}
So far, I have only tested this with MSVC (it works), but not with haskell
platform's mingw (which includes windows.h - so I would have to wait for
this...)
In my cabal file I have:
c-sources: mouse.c
So that basically sums up what I have, I just don't know how to do this. The
cabal documentation says for this directive:
c-sources: filename list
A list of C source files to be compiled and linked with the Haskell files.
Which is what I expected it to do - but to no avail.
I should note that when I try to comment out with -- the c-sources line I get
this:
Linking dist\build\BoardGames\BoardGames.exe ...
dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0x27d): undefined
reference to `__stginit_Mouse_'
dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0xb4): undefined
reference to `Mouse_a1_info'
dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0xcc): undefined
reference to `Mouse_czusetupConsole_info'
dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0xf8): undefined
reference to `Mouse_a1_info'
dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.text+0x17a): undefined
reference to `Mouse_czusetupConsole_info'
dist\build\BoardGames\BoardGames-tmp\Main.o:fake:(.data+0x14): undefined
reference to `Mouse_a1_closure'
collect2: ld returned 1 exit status
Any help that can be offered would be appreciated.
I would tell you where to find the project, but patch-tag is being unavailable
for me at this time. It is the 'BoardGames' project, under iaefai.
Thank you again,
iaefai.
------------------------------
Message: 5
Date: Mon, 23 Nov 2009 06:31:05 -0800 (PST)
From: Dominic Sim <dskw...@yahoo.com>
Subject: [Haskell-beginners] Retrieving the decimal portion of a
Double
To: beginners@haskell.org
Message-ID: <226442.15547...@web34506.mail.mud.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"
Hi all,
I am trying to retrieve the decimal portion of a Double. My code is:
getDecimal x = x - floor(x)
I would expect the following:
Main> getDecimal 1.23
0.23 :: [Double]
but instead, I get:
Main> getDecimal 1.23
ERROR - Unresolved overloading
*** Type : (RealFrac a, Integral a) => a
*** Expression : getDecimal 1.23
I have tried adding "getDecimal :: Double -> Double" but it only causes the
following message to appear:
ERROR file:C:\Documents and Settings\User\file.hs:60 - Instance of Integral
Double required for definition of getDecimal
How should I define my function so that it'll work? Thanks!
Regards,
Dom
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------------------------------
Message: 6
Date: Mon, 23 Nov 2009 08:45:00 -0700
From: Shawn Willden <shawn-hask...@willden.org>
Subject: Re: [Haskell-beginners] Retrieving the decimal portion of a
Double
To: beginners@haskell.org
Message-ID: <200911230845.00819.shawn-hask...@willden.org>
Content-Type: text/plain; charset="utf-8"
On Monday 23 November 2009 07:31:05 am Dominic Sim wrote:
> Â Â Â I am trying to retrieve the decimal portion of a Double. My code is:
>
> Â Â Â getDecimal x = x - floor(x)
The problem is that x is a double (or some other kind of floating point or
fraction), and "floor x" is an integer, and you can't subtract an integer
from a double. To convert "floor x" to a double (or to any other relevant
type), use "fromIntegral", like:
getDecimal x = x - fromIntegral(floor x)
However, what I'd really suggest is that you use:
getDecimal x = snd (properFraction x)
or, in pointfree style:
getDecimal = snd . properFraction
Also, the type signature for getDecimal should be:
getDecimal :: RealFrac a => a -> a
That will allow it to be used with any Real or Fractional type.
Shawn.
------------------------------
Message: 7
Date: Mon, 23 Nov 2009 12:08:46 -0800
From: Joe Van Dyk <j...@fixieconsulting.com>
Subject: [Haskell-beginners] recommended way to get haskell 6.10
installed on ubuntu hardy?
To: beginners@haskell.org
Message-ID:
<c715e640911231208w6cbc061dh58a74a530d532...@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
There's no ubuntu package for 6.10 (only 6.8), and the haskell
platform says you need 6.10 installed to build the source package.
--
Joe Van Dyk
http://fixieconsulting.com
------------------------------
Message: 8
Date: Tue, 24 Nov 2009 06:12:23 +1000
From: Tony Morris <tonymor...@gmail.com>
Subject: Re: [Haskell-beginners] recommended way to get haskell 6.10
installed on ubuntu hardy?
To: Joe Van Dyk <j...@fixieconsulting.com>
Cc: beginners@haskell.org
Message-ID: <4b0aeca7.2080...@gmail.com>
Content-Type: text/plain; charset=UTF-8
Hi Joe,
You might consider installing the 6.8 package to bootstrap a 6.10
compile. I've done it a few times with high success and pretty
straight-forward.
Joe Van Dyk wrote:
> There's no ubuntu package for 6.10 (only 6.8), and the haskell
> platform says you need 6.10 installed to build the source package.
>
>
>
>
--
Tony Morris
http://tmorris.net/
------------------------------
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