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Today's Topics:
1. Re: Is haskell a good choice for someone, who never
programmed before? (Marc Weber)
2. Re: Is haskell a good choice for someone, who never
programmed before? (Daniel Fischer)
3. Re: Re: multreplace (Patrick LeBoutillier)
4. Re: Is haskell a good choice for someone, who never
programmed before? (prad)
5. Re: Re: multreplace (Daniel Fischer)
6. Re: Is haskell a good choice for someone, who never
programmed before? (edgar klerks)
7. Re: Re: Is haskell a good choice for someone, who never
programmed before? (Marc Weber)
8. Re: upgrade Hackage show to QuickCheck 2 for lambdabot
(Antoine Latter)
----------------------------------------------------------------------
Message: 1
Date: Fri, 02 Jul 2010 22:59:22 +0200
From: Marc Weber <[email protected]>
Subject: Re: [Haskell-beginners] Is haskell a good choice for someone,
who never programmed before?
To: beginners <[email protected]>
Message-ID: <1278104050-sup-5...@nixos>
Content-Type: text/plain; charset=UTF-8
Hi Edgar
If he doesn't know any other languages it may be even easier to him.
Everyone who learned Basic and wants to start with Haskell has to change
his mind.
That said the only reason not to learn Haskell is
- there are existing solutions which work
- you want to use existing Java / .net libraries
- You want to target Flash or JavaScript only
(or something like that)
Nothing of that applies.
I'd even say Haskell is nice for beginning because if something compiles
it usually works (unless you hit advanced issues).
> but I don't want to scare him away.
Either he is scared or he is not. That won't depend on Haskell IMHO.
> And mathematics, where to start?
Ask him what he is interested in most. Start with that. Ask him what he
wants to do ..
If you have answers to that question Haskellers can help you easier and
point you in the right direction.
Greetings
Marc Weber
------------------------------
Message: 2
Date: Fri, 2 Jul 2010 23:05:21 +0200
From: Daniel Fischer <[email protected]>
Subject: Re: [Haskell-beginners] Is haskell a good choice for someone,
who never programmed before?
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
On Friday 02 July 2010 22:59:22, Marc Weber wrote:
> If you have answers to that question Haskellers can help you easier and
> point you in the right direction.
That reminds me of another point: The community. You won't easily find a
community nearly as helpful as the Haskell community.
------------------------------
Message: 3
Date: Fri, 2 Jul 2010 17:15:22 -0400
From: Patrick LeBoutillier <[email protected]>
Subject: Re: [Haskell-beginners] Re: multreplace
To: [email protected]
Message-ID:
<[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
> multRepl = foldl (uncurry . replace)
Actually I've been thinking about this and I can't quite figure out
how it works:
I understand the type of replace is
replace :: (Eq a) => [a] -> [a] -> [a] -> [a]
but I can't figure out how the type of (uncurry . replace) becomes
uncurry . replace :: (Eq a) => [a] -> ([a], [a]) -> [a]
?
Patrick
--
=====================
Patrick LeBoutillier
Rosemère, Québec, Canada
------------------------------
Message: 4
Date: Fri, 2 Jul 2010 14:28:40 -0700
From: prad <[email protected]>
Subject: [Haskell-beginners] Re: Is haskell a good choice for someone,
who never programmed before?
To: [email protected]
Message-ID: <20100702142840.14790...@gom>
Content-Type: text/plain; charset=US-ASCII
On Fri, 2 Jul 2010 22:36:46 +0200
edgar klerks <[email protected]> wrote:
> Is haskell a good choice for someone, who never programmed before?
>
as a recent haskell newbie myself i would say definitely yes! my minor
programming experience is just getting in the way.
marc weber wrote:
"Everyone who learned Basic and wants to start with Haskell has to
change his mind."
my god yes!
i find i'm actually having to learn programming concepts properly. i
can't just sit down and create a script through trial and error. :D
a mind replacement would likely be better for me than a simple change,
but i'll settle for the latter for now.
daniel fischer wrote:
"You won't easily find a community nearly as helpful as the Haskell
community."
having been on several excellent boards for various computer oriented
issues, i can with, without hesitation, state that this community is
the best i've come across.
when i ask a question, i'm not just given an answer ... i'm provided
with a technical paper with tips, ideas, details unparallelled to
anything else i've seen on any forum i've frequented over the past
decade. (actually, edgar you are a case in point, since you were the
first to assist me).
the entire spirit is different here!
--
In friendship,
prad
... with you on your journey
Towards Freedom
http://www.towardsfreedom.com (website)
Information, Inspiration, Imagination - truly a site for soaring I's
------------------------------
Message: 5
Date: Fri, 2 Jul 2010 23:30:18 +0200
From: Daniel Fischer <[email protected]>
Subject: Re: [Haskell-beginners] Re: multreplace
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
On Friday 02 July 2010 23:15:22, Patrick LeBoutillier wrote:
> > multRepl = foldl (uncurry . replace)
>
> Actually I've been thinking about this and I can't quite figure out
> how it works:
>
> I understand the type of replace is
>
> replace :: (Eq a) => [a] -> [a] -> [a] -> [a]
>
> but I can't figure out how the type of (uncurry . replace) becomes
>
> uncurry . replace :: (Eq a) => [a] -> ([a], [a]) -> [a]
>
> ?
let's make it
foo :: a -> b -> c -> d
to not get confused by the fact that replace's arguments and result all
have the same type.
So, what does uncurry . foo do?
Well, (f . g) x = f (g x), so when we apply (uncurry . foo) to an argument
x, we get
uncurry (foo x)
Now, x is the first argument of foo, so x :: a, and
(foo x) :: b -> c -> d
That means (foo x) has just the type uncurry expects, hence
uncurry (foo x) :: (b, c) -> d
Now write uncurry (foo x) again as
(uncurry . foo) x :: (b, c) -> d
and remove x again, so
(uncurry . foo) :: a -> (b, c) -> d
finally, remember that foo is actually replace and hence all four type
variables stand for the same list type (with an Eq constraint).
>
>
> Patrick
------------------------------
Message: 6
Date: Fri, 2 Jul 2010 23:32:55 +0200
From: edgar klerks <[email protected]>
Subject: Re: [Haskell-beginners] Is haskell a good choice for someone,
who never programmed before?
To: Daniel Fischer <[email protected]>, [email protected]
Cc: [email protected]
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Hi Marc and Daniel,
On Fri, Jul 2, 2010 at 10:50 PM, Daniel Fischer <[email protected]>wrote:
> On Friday 02 July 2010 22:36:46, edgar klerks wrote:
> > Hi All,
> >
> > I have a question. A friend of mine wants to learn a programming
> > language, because we work together. He studied economics and is busy in
> > the financial sector. I understood Haskell is used there pretty much, so
> > he got interested in it. But is haskell a good language for someone, who
> > never even tried a language like basic?
>
> Actually, the rumour goes that Haskell is easier to learn if your brain
> hasn't been conditioned by years of imperative programming.
>
>
I know, I don't want to be sour, but when I started to learn haskell it
almost hurt. I took me a couple of months to loose the imperative style of
thought. I have a physics background and picked up programming along the
way. For some reason they never used functional languages. Such a pity.
But now it is backwards, every time I have to go back to imperative style or
something alike I am kinda bored. Luckily I slowly start to find it easier
to implement stuff in Haskell instead of in other languages.
But it is true, that you have to unlearn yourself. And for some reason I
feel functional languages have the future.
I think haskell has some points over lisp, because there is a lot of noise
in the latter with the ()'s.
Marc Weber <[email protected]> wrote:
Ask him what he is interested in most. Start with that. Ask him what he
> wants to do ..
> If you have answers to that question Haskellers can help you easier and
> point you in the right direction.
>
> He is interested in econometrics, I don't know much about it. I understood
they use a lot of linear algebra. I have some books and sylabi about that,
but more pointed towards physics.
On Friday 02 July 2010 22:59:22, Marc Weber wrote:
> If you have answers to that question Haskellers can help you easier and
> point you in the right direction.
That reminds me of another point: The community. You won't easily find a
community nearly as helpful as the Haskell community.
That is true, this one of the most helpful communities I encountered.
Haskell programmers seems also to be more knowledgeable than other
programmers in maths.
I bought 2 books now:
The road to haskell, logic and mathematics.
Simon Thompson's Craft of Functional Programming
And I have Real world haskell lying around, but I lend it to someone else. I
am "poisoning" my environment with haskell at the moment. :) I am a start up
in the financial business. And one of the further goals is to develop
financial tools for small and middle sized business. (Now we have some
projects, which should induce a cash flow. Hopefully) Therefore the guy has
to understand, what Haskell can do.
I shall try to find out, what direction of mathematics interest him the
most.
Tnx for your help!
Edgar
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Message: 7
Date: Sat, 03 Jul 2010 00:32:38 +0200
From: Marc Weber <[email protected]>
Subject: Re: [Haskell-beginners] Re: Is haskell a good choice for
someone, who never programmed before?
To: beginners <[email protected]>
Message-ID: <1278109831-sup-9...@nixos>
Content-Type: text/plain; charset=UTF-8
If you'd ask me only I'd eventually say that you should know both worlds
today .. At least a little bit. It always depends on the use case.
Marc Weber
------------------------------
Message: 8
Date: Fri, 2 Jul 2010 18:09:59 -0500
From: Antoine Latter <[email protected]>
Subject: Re: [Haskell-beginners] upgrade Hackage show to QuickCheck 2
for lambdabot
To: Mark Wright <[email protected]>
Cc: [email protected], haskell mailing list
<[email protected]>
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="utf-8"
Including the café.
On Jul 2, 2010 8:49 AM, "Mark Wright" <[email protected]> wrote:
Hi,
I'm trying to upgrade Hackage show to QuickCheck 2, after
applying the diffs below (which may not be correct, since I am
a beginner), I am left which this error message:
runghc ./Setup.hs build
Preprocessing library show-0.3.4...
Building show-0.3.4...
[4 of 4] Compiling ShowQ ( ShowQ.hs, dist/build/ShowQ.o )
ShowQ.hs:104:20: Not in scope: `generate'
Compilation exited abnormally with code 1 at Fri Jul 2 23:07:17
The error occurs in this method:
tests :: Gen Result -> StdGen -> Int -> Int -> [[String]] -> IO String
tests gen rnd0 ntest nfail stamps
| ntest == 500 = done "OK, passed" ntest stamps
| nfail == 1000 = done "Arguments exhausted after" ntest stamps
| otherwise = case ok result of
Nothing -> tests gen rnd1 ntest (nfail+1) stamps
Just True -> tests gen rnd1 (ntest+1) nfail (stamp result:stamps)
Just False -> return $ "Falsifiable, after "
++ show ntest
++ " tests:\n"
++ reason result
where
result = generate (((+ 3) . (`div` 2)) ntest) rnd2 gen
(rnd1,rnd2) = split rnd0
The QuickCheck 1 generate method is near the bottom this page:
http://hackage.haskell.org/packages/archive/QuickCheck/1.2.0.0/doc/html/Test-QuickCheck.html
but I can not find generate in QuickCheck 2. I am wondering if
you have any ideas on how to fix it?
I'm trying to package lambdabot on Solaris. I have already packaged
the Haskell Platform and about 90 packages, they are in:
http://pkgbuild.sourceforge.net/spec-files-extra/
Thanks very much, Mark
here are the diffs:
goanna% diff -wc show-0.3.4-orig/ShowQ.hs show-0.3.4/ShowQ.hs
*** show-0.3.4-orig/ShowQ.hs Wed Jan 20 11:24:11 2010
--- show-0.3.4/ShowQ.hs Fri Jul 2 23:07:13 2010
***************
*** 12,22 ****
--- 12,25 ----
import qualified Test.SmallCheck (smallCheck, Testable)
import Test.QuickCheck
+ import Test.QuickCheck.Arbitrary
import Data.Char
import Data.List
import Data.Word
import Data.Int
import System.Random
+ import Control.Exception (evaluate)
+ import Test.QuickCheck.Property (ok, stamp)
type T = [Int]
type I = Int
***************
*** 23,36 ****
--- 26,45 ----
instance Arbitrary Char where
arbitrary = choose (minBound, maxBound)
+
+ instance CoArbitrary Char where
coarbitrary c = variant (ord c `rem` 4)
instance Arbitrary Word8 where
arbitrary = choose (minBound, maxBound)
+
+ instance CoArbitrary Word8 where
coarbitrary c = variant (fromIntegral ((fromIntegral c) `rem` 4))
instance Arbitrary Ordering where
arbitrary = elements [LT,EQ,GT]
+
+ instance CoArbitrary Ordering where
coarbitrary LT = variant 1
coarbitrary EQ = variant 2
coarbitrary GT = variant 0
***************
*** 37,42 ****
--- 46,53 ----
instance Arbitrary Int64 where
arbitrary = sized $ \n -> choose (-fromIntegral n,fromIntegral n)
+
+ instance CoArbitrary Int64 where
coarbitrary n = variant (fromIntegral (if n >= 0 then 2*n else 2*(-n) +
1))
instance (Integral a, Arbitrary a) => Arbitrary (Ratio a) where
***************
*** 48,53 ****
--- 59,65 ----
else (b % a)
else (a % b)
+ instance (Integral a, CoArbitrary a) => CoArbitrary (Ratio a) where
coarbitrary m = variant (fromIntegral $ if n >= 0 then 2*n else 2*(-n) +
1)
where n = numerator m
***************
*** 87,93 ****
Just False -> return $ "Falsifiable, after "
++ show ntest
++ " tests:\n"
! ++ unlines (arguments result)
where
result = generate (((+ 3) . (`div` 2)) ntest) rnd2 gen
(rnd1,rnd2) = split rnd0
--- 99,105 ----
Just False -> return $ "Falsifiable, after "
++ show ntest
++ " tests:\n"
! ++ reason result
where
result = generate (((+ 3) . (`div` 2)) ntest) rnd2 gen
(rnd1,rnd2) = split rnd0
goanna%
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