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Today's Topics:
1. Re: Why is there no notion of a one-tuple (e.g., a '([])' as
opposed to a '[]') in Haskell? (Jason Dusek)
2. Re: Why is there no notion of a one-tuple (e.g., a '([])' as
opposed to a '[]') in Haskell? (Benjamin L.Russell)
3. Re: Why is there no notion of a one-tuple (e.g., a '([])' as
opposed to a '[]') in Haskell? (Aaron Denney)
4. Module import problem (Casey Rodarmor)
5. Re: Module import problem (Chry Cheng)
6. Re: Module import problem (Casey Rodarmor)
7. Re: Module import problem (Christian Cheng)
8. Re: Module import problem ( Chadda? Fouch? )
----------------------------------------------------------------------
Message: 1
Date: Thu, 25 Sep 2008 00:56:26 -0700
From: "Jason Dusek" <[EMAIL PROTECTED]>
Subject: Re: [Haskell-beginners] Why is there no notion of a one-tuple
(e.g., a '([])' as opposed to a '[]') in Haskell?
To: "Benjamin L. Russell" <[EMAIL PROTECTED]>
Cc: beginners@haskell.org
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset=UTF-8
How is a 1-tuple different from a value? If we think of tuple
types as product types, then the 1-ary product is a simple
type -- and 1-ary tuples of values are simple values.
In Python, tuples really are like lists -- to the point of
being mapable, iterable, &c. In Haskell, lists and tuples
share very little.
--
_jsn
------------------------------
Message: 2
Date: Thu, 25 Sep 2008 19:14:45 +0900
From: Benjamin L.Russell <[EMAIL PROTECTED]>
Subject: [Haskell-beginners] Re: Why is there no notion of a one-tuple
(e.g., a '([])' as opposed to a '[]') in Haskell?
To: beginners@haskell.org
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset=us-ascii
On Wed, 24 Sep 2008 21:27:37 -0400, [EMAIL PROTECTED] wrote:
>G'day all.
>
>Quoting "Benjamin L.Russell" <[EMAIL PROTECTED]>:
>
>>> Haskell doesn't have a notion of a one-element tuple.
>>
>> Why not?
>
>As noted by others, there's no syntactic space for them.
>
>Perhaps more crucially, it's hard to see where such a thing would
>be useful. The 2-tuple (i.e. pair) is a categorical product, and can
>be used to carry around two things where you would normally only
>have space for one. The 0-tuple (i.e. void) is a categorical terminal
>object, and can be used to fill in space in a parametric data structure
>where no annotation is actually needed.
>
>One reason why they're provided in the Prelude is so that standard
>functions can do operations on them. It's hard to see where a standard
>function would use a generic 1-tuple.
>
>Generally speaking, if you need a type-checked 1-tuple, you almost
>certainly don't want a generic one.
So, basically generic one-element tuples don't exist because they're
not needed, and there is no elegant way to represent them
syntactically.
That makes sense.
Nevertheless, I can't help feeling that Haskell could perhaps been
made even more elegant if some alternative tuple notation not
conflicting with parentheses had been used; e.g., '{}' (braces)
(please forgive me if braces are already used for some other purpose
of which I am not aware). Then, for example, we could have the
following:
{} (a unit, or void),
{{}} (a one-tuple),
{{{}}} (a one-tuple consisting of a one-tuple),
{{{{}}}} (a one-tuple consisting of a one-tuple consisting of a
one-tuple),
...
We could then come up with an n-depth-ordering on tuples, as opposed
to an ordering on n-tuples. While perhaps not immediately useful,
this ordering would have an interesting structure, and perhaps lead to
some kind of mathematics of n-depth-orderings, which could be even
more interesting, and which could be expressed in Haskell.
-- Benjamin L. Russell
------------------------------
Message: 3
Date: Wed, 24 Sep 2008 23:26:33 +0000 (UTC)
From: Aaron Denney <[EMAIL PROTECTED]>
Subject: [Haskell-beginners] Re: Why is there no notion of a one-tuple
(e.g., a '([])' as opposed to a '[]') in Haskell?
To: beginners@haskell.org
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset=us-ascii
On 2008-09-24, Benjamin L.Russell <[EMAIL PROTECTED]> wrote:
>>Haskell doesn't have a notion of a one-element tuple.
>
> Why not?
In addition to the syntactic nightmare mentioned, or the possible loss
of parenthesized expressions, it's just plain not necessary. Aside from
strictness, a one-tuple is isomorphic to the element inside. We like
category theory, so we ignore trivial isomorphisms.
--
Aaron Denney
-><-
------------------------------
Message: 4
Date: Sun, 28 Sep 2008 17:32:02 +0200
From: "Casey Rodarmor" <[EMAIL PROTECTED]>
Subject: [Haskell-beginners] Module import problem
To: beginners@haskell.org
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset=ISO-8859-1
Hi there!
I have a problem with importing a module I'd like to use.
My working directory, ~/proj, contains:
./Haskore -- a folder containing a version of haskore, this music thingy
./test.hs -- random stuff using haskore
The main file in ~/proj/Haskore is ~/proj/Haskore/Haskore.hs, which
contains the following module declaration:
> module Haskore(module HaskoreLoader) where
> import HaskoreLoader
I've tried to put all the following in ~/proj/test.hs, with no luck:
> import Haskore -- Could not find module `Haskore':
> import Haskore.Haskore -- file name does not match module name `Haskore'
Am I doing something wrong? Is there a way to place a module in an
arbitrary directory, without having to modify it?
Thanks so much for your help!
Best,
Casey Rodarmor
------------------------------
Message: 5
Date: Mon, 29 Sep 2008 00:08:23 +0800
From: Chry Cheng <[EMAIL PROTECTED]>
Subject: Re: [Haskell-beginners] Module import problem
To: "Casey Rodarmor" <[EMAIL PROTECTED]>
Cc: beginners@haskell.org
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset=us-ascii
"Casey Rodarmor" <[EMAIL PROTECTED]> writes:
> Hi there!
>
> I have a problem with importing a module I'd like to use.
>
> My working directory, ~/proj, contains:
> ./Haskore -- a folder containing a version of haskore, this music thingy
> ./test.hs -- random stuff using haskore
>
> The main file in ~/proj/Haskore is ~/proj/Haskore/Haskore.hs, which
> contains the following module declaration:
>> module Haskore(module HaskoreLoader) where
>> import HaskoreLoader
>
> I've tried to put all the following in ~/proj/test.hs, with no luck:
>> import Haskore -- Could not find module `Haskore':
>> import Haskore.Haskore -- file name does not match module name `Haskore'
>
> Am I doing something wrong? Is there a way to place a module in an
> arbitrary directory, without having to modify it?
>
> Thanks so much for your help!
>
> Best,
> Casey Rodarmor
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
You have to tell GHC where to find Haskore. To do this, call ghc with the i
option:
ghc -iHaskore/
then, import using:
import Haskore
------------------------------
Message: 6
Date: Sun, 28 Sep 2008 18:20:25 +0200
From: "Casey Rodarmor" <[EMAIL PROTECTED]>
Subject: Re: [Haskell-beginners] Module import problem
Cc: beginners@haskell.org
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset=ISO-8859-1
On Sun, Sep 28, 2008 at 6:08 PM, Chry Cheng <[EMAIL PROTECTED]> wrote:
> "Casey Rodarmor" <[EMAIL PROTECTED]> writes:
>
>> Hi there!
>>
>> I have a problem with importing a module I'd like to use.
>>
>> My working directory, ~/proj, contains:
>> ./Haskore -- a folder containing a version of haskore, this music thingy
>> ./test.hs -- random stuff using haskore
>>
>> The main file in ~/proj/Haskore is ~/proj/Haskore/Haskore.hs, which
>> contains the following module declaration:
>>> module Haskore(module HaskoreLoader) where
>>> import HaskoreLoader
>>
>> I've tried to put all the following in ~/proj/test.hs, with no luck:
>>> import Haskore -- Could not find module `Haskore':
>>> import Haskore.Haskore -- file name does not match module name `Haskore'
>>
>> Am I doing something wrong? Is there a way to place a module in an
>> arbitrary directory, without having to modify it?
>>
>> Thanks so much for your help!
>>
>> Best,
>> Casey Rodarmor
>> _______________________________________________
>> Beginners mailing list
>> Beginners@haskell.org
>> http://www.haskell.org/mailman/listinfo/beginners
>
> You have to tell GHC where to find Haskore. To do this, call ghc with the i
> option:
>
> ghc -iHaskore/
>
> then, import using:
>
> import Haskore
>
Hi Chry,
Thanks for the answer, everything works now :-)
I must admit, I'm a little disappointed if that's the only way to get
it to work. On the surface of things, I don't see why one can't just
put a Module in some/arbitrary/directory, and then import it as
some.arbitrary.directory.Module. The need to use a flag on the command
line seems a little unnecessary.
Can anyone give a little insight into why this decision was made?
Best,
Casey
------------------------------
Message: 7
Date: Mon, 29 Sep 2008 01:33:34 +0800
From: "Christian Cheng" <[EMAIL PROTECTED]>
Subject: Re: [Haskell-beginners] Module import problem
To: "Casey Rodarmor" <[EMAIL PROTECTED]>
Cc: beginners@haskell.org
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset=ISO-8859-1
On Mon, Sep 29, 2008 at 12:20 AM, Casey Rodarmor
<[EMAIL PROTECTED]> wrote:
>
> On Sun, Sep 28, 2008 at 6:08 PM, Chry Cheng <[EMAIL PROTECTED]> wrote:
> > "Casey Rodarmor" <[EMAIL PROTECTED]> writes:
> >
> >> Hi there!
> >>
> >> I have a problem with importing a module I'd like to use.
> >>
> >> My working directory, ~/proj, contains:
> >> ./Haskore -- a folder containing a version of haskore, this music thingy
> >> ./test.hs -- random stuff using haskore
> >>
> >> The main file in ~/proj/Haskore is ~/proj/Haskore/Haskore.hs, which
> >> contains the following module declaration:
> >>> module Haskore(module HaskoreLoader) where
> >>> import HaskoreLoader
> >>
> >> I've tried to put all the following in ~/proj/test.hs, with no luck:
> >>> import Haskore -- Could not find module `Haskore':
> >>> import Haskore.Haskore -- file name does not match module name `Haskore'
> >>
> >> Am I doing something wrong? Is there a way to place a module in an
> >> arbitrary directory, without having to modify it?
> >>
> >> Thanks so much for your help!
> >>
> >> Best,
> >> Casey Rodarmor
> >> _______________________________________________
> >> Beginners mailing list
> >> Beginners@haskell.org
> >> http://www.haskell.org/mailman/listinfo/beginners
> >
> > You have to tell GHC where to find Haskore. To do this, call ghc with the
> > i option:
> >
> > ghc -iHaskore/
> >
> > then, import using:
> >
> > import Haskore
> >
>
> Hi Chry,
>
> Thanks for the answer, everything works now :-)
>
> I must admit, I'm a little disappointed if that's the only way to get
> it to work. On the surface of things, I don't see why one can't just
> put a Module in some/arbitrary/directory, and then import it as
> some.arbitrary.directory.Module. The need to use a flag on the command
> line seems a little unnecessary.
>
I beg to differ. I don't think it's reasonable to expect the compiler
to figure out on its own where we have stashed additional classes.
Other programming languages have a similar requirement. For Java,
it's the class path (e.g., javac -classpath Haskore); C/C++, the
include directories (IIRC, gcc -I Haskore), etc.
> Can anyone give a little insight into why this decision was made?
>
> Best,
> Casey
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://www.haskell.org/mailman/listinfo/beginners
------------------------------
Message: 8
Date: Sun, 28 Sep 2008 19:35:19 +0200
From: " Chadda? Fouch? " <[EMAIL PROTECTED]>
Subject: Re: [Haskell-beginners] Module import problem
To: "Casey Rodarmor" <[EMAIL PROTECTED]>
Cc: beginners@haskell.org
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset=ISO-8859-1
2008/9/28 Casey Rodarmor <[EMAIL PROTECTED]>:
> I must admit, I'm a little disappointed if that's the only way to get
> it to work. On the surface of things, I don't see why one can't just
> put a Module in some/arbitrary/directory, and then import it as
> some.arbitrary.directory.Module. The need to use a flag on the command
> line seems a little unnecessary.
>
> Can anyone give a little insight into why this decision was made?
Because that's how every language worked for decades for good reasons
: a library usually stay in one place on the filesystem while several
projects from several locations try to use it. So of course we would
prefer for each of these projects source to refer to the library in
the same fashion, especially given that it can be moved later on or
split between different buildtree or ...
Now, you may not be aware of that but you can register a library so
that GHC always know where to find its module, as long as you use
--make on the command line : ghc --make myScript.hs .
--
Jedaï
------------------------------
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