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Today's Topics:
1. Re: Rank beginner question about debugging (Brent Yorgey)
2. Re: Double's (Brent Yorgey)
3. Re: Rank beginner question about debugging (Joe Fredette)
4. Re: Double's (Nicolas Pouillard)
5. Re: Double's (Felipe Lessa)
6. haskell problem (B1lal)
7. Re: haskell problem (Isaac Dupree)
8. Re: haskell problem (Felipe Lessa)
9. Re: haskell problem (Brent Yorgey)
----------------------------------------------------------------------
Message: 1
Date: Tue, 21 Jul 2009 22:43:30 -0400
From: Brent Yorgey <byor...@seas.upenn.edu>
Subject: Re: [Haskell-beginners] Rank beginner question about
debugging
To: beginners@haskell.org
Message-ID: <20090722024329.ga24...@seas.upenn.edu>
Content-Type: text/plain; charset=us-ascii
On Tue, Jul 21, 2009 at 09:26:19AM -0400, Ben Wise wrote:
> Folks,
>
> I'm a rank beginner in Haskell, and though Haskell seems like a great
> language to start using, I've got a serious concern about debugging.
>
> In about 15 years of Lisp experience, then 15 years of C++, I've gotten
> pretty accustomed to the idea of using a debugger with lots of pre- and
> post-conditions on functions, breakpoints, stack trace, and variable
> inspection -- even though it gets tricky with delayed evaluation,
> macros, etc. in Lisp!
If you think it's tricky in Lisp, it's about ten times as tricky with
a lazy language like Haskell! Using gdb with Haskell executables is
pretty much useless since the generated code doesn't correspond to the
Haskell code in any obvious ways. And it's really hard to make
traditional debuggers since the ghc runtime model looks nothing like
traditional ones. However, There IS a debugger built into most recent
versions of ghci which lets you do some of these things -- have you
taken a look at that?
I've done quite a bit of programming using the sort of debuggers you
describe myself---with C, C++, and Java in particular. And yet in all
the Haskell coding I've done over the past few years---some of it
quite significant---I've rarely missed those sorts of debuggers. I'm
not quite sure I understand the reason why. Perhaps it's partly
because Haskell lets you program on such a high level that there's
less room for the sorts of titchy errors that debuggers are so good at
helping you find. In any case, I wouldn't worry about it too much at
this point if I were you, and if you really do find yourself wanting
it, take a look at the ghci debugger.
-Brent
------------------------------
Message: 2
Date: Tue, 21 Jul 2009 22:45:29 -0400
From: Brent Yorgey <byor...@seas.upenn.edu>
Subject: Re: [Haskell-beginners] Double's
To: beginners@haskell.org
Message-ID: <20090722024529.gb24...@seas.upenn.edu>
Content-Type: text/plain; charset=us-ascii
On Tue, Jul 21, 2009 at 08:51:05PM -0300, Felipe Lessa wrote:
> On Tue, Jul 21, 2009 at 07:10:40PM -0400, Thomas Friedrich wrote:
> > I really should have thought about this, but I didn't.
>
> Note that Rational's are really really really slow, probably it
> would be better to spend some time reading Goldberg's paper[1].
>
> [1] http://docs.sun.com/source/806-3568/ncg_goldberg.html
Premature optimization is the sqrt of all evil.
-Brent
------------------------------
Message: 3
Date: Wed, 22 Jul 2009 01:09:42 -0400
From: Joe Fredette <jfred...@gmail.com>
Subject: Re: [Haskell-beginners] Rank beginner question about
debugging
To: Brent Yorgey <byor...@seas.upenn.edu>
Cc: beginners@haskell.org
Message-ID: <4a669f16.3070...@gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
I, for one, have never found a need for a more traditional debugger in
haskell. Most of my 'bugs' are more accurately described as 'behavior
which I did not intend' rather than the more normal description of
'behavior which breaks things'. That is, Haskell programs (almost)
always work if they type-check, however,
they may work in a way you had not planned on.
:)
/Joe
Brent Yorgey wrote:
> On Tue, Jul 21, 2009 at 09:26:19AM -0400, Ben Wise wrote:
>
>> Folks,
>>
>> I'm a rank beginner in Haskell, and though Haskell seems like a great
>> language to start using, I've got a serious concern about debugging.
>>
>> In about 15 years of Lisp experience, then 15 years of C++, I've gotten
>> pretty accustomed to the idea of using a debugger with lots of pre- and
>> post-conditions on functions, breakpoints, stack trace, and variable
>> inspection -- even though it gets tricky with delayed evaluation,
>> macros, etc. in Lisp!
>>
>
> If you think it's tricky in Lisp, it's about ten times as tricky with
> a lazy language like Haskell! Using gdb with Haskell executables is
> pretty much useless since the generated code doesn't correspond to the
> Haskell code in any obvious ways. And it's really hard to make
> traditional debuggers since the ghc runtime model looks nothing like
> traditional ones. However, There IS a debugger built into most recent
> versions of ghci which lets you do some of these things -- have you
> taken a look at that?
>
> I've done quite a bit of programming using the sort of debuggers you
> describe myself---with C, C++, and Java in particular. And yet in all
> the Haskell coding I've done over the past few years---some of it
> quite significant---I've rarely missed those sorts of debuggers. I'm
> not quite sure I understand the reason why. Perhaps it's partly
> because Haskell lets you program on such a high level that there's
> less room for the sorts of titchy errors that debuggers are so good at
> helping you find. In any case, I wouldn't worry about it too much at
> this point if I were you, and if you really do find yourself wanting
> it, take a look at the ghci debugger.
>
> -Brent
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
>
>
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Message: 4
Date: Wed, 22 Jul 2009 13:22:55 +0200
From: Nicolas Pouillard <nicolas.pouill...@gmail.com>
Subject: Re: [Haskell-beginners] Double's
To: Brent Yorgey <byor...@seas.upenn.edu>
Cc: beginners <beginners@haskell.org>
Message-ID: <1248261727-sup-6...@ausone.local>
Content-Type: text/plain; charset=UTF-8
Excerpts from Brent Yorgey's message of Wed Jul 22 04:45:29 +0200 2009:
> On Tue, Jul 21, 2009 at 08:51:05PM -0300, Felipe Lessa wrote:
> > On Tue, Jul 21, 2009 at 07:10:40PM -0400, Thomas Friedrich wrote:
> > > I really should have thought about this, but I didn't.
> >
> > Note that Rational's are really really really slow, probably it
> > would be better to spend some time reading Goldberg's paper[1].
> >
> > [1] http://docs.sun.com/source/806-3568/ncg_goldberg.html
>
> Premature optimization is the sqrt of all evil.
+1 Rationals can do their jobs really well, even being much slower than
Doubles.
--
Nicolas Pouillard
http://nicolaspouillard.fr
------------------------------
Message: 5
Date: Wed, 22 Jul 2009 09:23:26 -0300
From: Felipe Lessa <felipe.le...@gmail.com>
Subject: Re: [Haskell-beginners] Double's
To: beginners@haskell.org
Message-ID: <20090722122326.ga28...@kira.casa>
Content-Type: text/plain; charset=us-ascii
On Tue, Jul 21, 2009 at 10:45:29PM -0400, Brent Yorgey wrote:
> On Tue, Jul 21, 2009 at 08:51:05PM -0300, Felipe Lessa wrote:
> > Note that Rational's are really really really slow, probably it
>
> Premature optimization is the sqrt of all evil.
I agree, however statistics tend to be very math intensive, and
even in simple cases you may end up with a big numerator and a
big denominator, totally thrashing your performance. He could
write all his functions as taking a (Num a), which would let him
choose between both, but if he wants to do that then he must
learn how to handle the subtleties of Doubles.
(Also Rationals don't support a lot of useful functions like
sqrt itself or exp.)
--
Felipe.
------------------------------
Message: 6
Date: Wed, 22 Jul 2009 19:21:56 +0100
From: "B1lal" <hbk1_h...@hotmail.com>
Subject: [Haskell-beginners] haskell problem
To: <beginners@haskell.org>
Message-ID: <snt112-ds21b2791efad7a83cea8c7990...@phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"
im having problem with this Haskell functions
female, male :: String -> Bool
for finding out the gender for a given name which can be inferred from the
title.
For example,
gender> female "Ms. Green"
True
gender> female "King Arthur"
False
gender> male "Mr. Scrooge"
True
gender> female "Miss Beatrix Potter"
True
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Message: 7
Date: Wed, 22 Jul 2009 23:01:24 -0400
From: Isaac Dupree <m...@isaac.cedarswampstudios.org>
Subject: Re: [Haskell-beginners] haskell problem
To: B1lal <hbk1_h...@hotmail.com>
Cc: beginners@haskell.org
Message-ID: <4a67d284.5050...@isaac.cedarswampstudios.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
B1lal wrote:
> im having problem with this Haskell functions
> female, male :: String -> Bool
>
> for finding out the gender for a given name which can be inferred from the
> title.
Are you trying to implement it? Have you tried Data.List.isPrefixOf? Are
you aware of just how many different titles there are in the world, both
gender-specific and non-gender-specific (although admittedly fewer and
less ambiguous than it is for names)?...Probably some of them will
appear after someone's name rather than before, too, and then you get to
play with fun contradictory things like "Madam So-and-so, Prince of
Wales". This smells like a fishy thing to do, I suppose it's like
homework rather than the real world...?
P.S. gender discrimination! :-P
-Isaac
------------------------------
Message: 8
Date: Thu, 23 Jul 2009 00:11:47 -0300
From: Felipe Lessa <felipe.le...@gmail.com>
Subject: Re: [Haskell-beginners] haskell problem
To: beginners@haskell.org
Message-ID: <20090723031147.ga21...@kira.casa>
Content-Type: text/plain; charset=us-ascii
On Wed, Jul 22, 2009 at 07:21:56PM +0100, B1lal wrote:
> im having problem with this Haskell functions
> female, male :: String -> Bool
female = not . male
male = not . female
:)
--
Felipe.
------------------------------
Message: 9
Date: Thu, 23 Jul 2009 00:11:15 -0400
From: Brent Yorgey <byor...@seas.upenn.edu>
Subject: Re: [Haskell-beginners] haskell problem
To: beginners@haskell.org
Message-ID: <20090723041115.ga25...@seas.upenn.edu>
Content-Type: text/plain; charset=us-ascii
On Wed, Jul 22, 2009 at 07:21:56PM +0100, B1lal wrote:
> im having problem with this Haskell functions
> female, male :: String -> Bool
>
> for finding out the gender for a given name which can be inferred from the
> title.
>
> For example,
>
> gender> female "Ms. Green"
>
> True
>
> gender> female "King Arthur"
>
> False
>
> gender> male "Mr. Scrooge"
>
> True
>
> gender> female "Miss Beatrix Potter"
>
> True
What have you tried so far? What specifically are you having problems
with? This sounds a lot like a homework problem; we are happy to help
you with specific problems but in general we won't do your homework
for you.
-Brent
------------------------------
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