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Today's Topics:
1. Re: phantom type (PICCA Frederic-Emmanuel)
2. Re: phantom type (PICCA Frederic-Emmanuel)
3. Re: Efficient Binary Multiplication (Stephen Tetley)
4. Re: Efficient Binary Multiplication (KC)
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Message: 1
Date: Wed, 18 Apr 2018 14:39:58 +0000
From: PICCA Frederic-Emmanuel
<frederic-emmanuel.pi...@synchrotron-soleil.fr>
To: "The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell" <beginners@haskell.org>
Subject: Re: [Haskell-beginners] phantom type
Message-ID:
<a2a20ec3b8560d408356cac2fc148e530107ded...@sun-dag4.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
> Directly relevant blog:
> https://www.benjamin.pizza/posts/2017-12-15-functor-functors.html
thanks a lot very interesting post :)
------------------------------
Message: 2
Date: Wed, 18 Apr 2018 14:41:39 +0000
From: PICCA Frederic-Emmanuel
<frederic-emmanuel.pi...@synchrotron-soleil.fr>
To: "The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell" <beginners@haskell.org>
Subject: Re: [Haskell-beginners] phantom type
Message-ID:
<a2a20ec3b8560d408356cac2fc148e530107ded...@sun-dag4.synchrotron-soleil.fr>
Content-Type: text/plain; charset="us-ascii"
Hello
> I am in a rush so I cant write a minimal example, but wouldn't
> a typeclass + make Collect and Cara instances of that typeclass do?
Yes I can do this in my case and it is not thaht difficult :).
thanks for your help.
cheers
Frederic
------------------------------
Message: 3
Date: Wed, 18 Apr 2018 18:33:12 +0100
From: Stephen Tetley <stephen.tet...@gmail.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: Re: [Haskell-beginners] Efficient Binary Multiplication
Message-ID:
<CAB2TPRB_VrjCThcvSyVE-toFdUhi_tspTMpzN=TB3jE=ss4...@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
List fusion has existed for a long time (based on a change to the
internal representation of lists to make them streams).
IIRC the actual implementation was not considered a satisfactory
replacement for GHCs existing list implementation as performance
improvements were not uniform, the stream representation is good for
some things worse for others. I don't know whether this situation has
now changed.
Byte String and Text exist because implementing strings or byte
sequences as a cons list of Char or Byte is very inefficient both for
storage / data locality and for many operations. Fusion for Byte
String and Text is a bonus rather than a motivation.
[*] Stream Fusion: From Lists to Streams to Nothing at All
Duncan Coutts , Roman Leshchinskiy , Don Stewart
http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.104.7401
On 17 April 2018 at 01:48, Steven Leiva <leiva.ste...@gmail.com> wrote:
> Interesting question.
>
> So there is a concept in computer science called fusion.
>
> My understanding (I don't have a CS degree) is that when data is subject to
> fusion, we don't create the intermediary lists as you are talking about.
> This is why, in Haskell, we have the ByteString and Text datatypes. Unlike
> String, they (ByteString / Text) are subject to fusion. Text is useful when
> we are dealing with unicode data, while ByteString is the correct tool when
> we are dealing with binary data.
>
> All of this is to say that you should look at the ByteString data type.
> (Take a look at this description, for example:
> https://hackage.haskell.org/package/bytestring-0.10.8.2/docs/Data-ByteString.html#t:ByteString).
>
> The only potential problem I see is that ByteString internally uses Word8,
> and since Word8 is unsigned, negatives are problematic. (Now that I think
> about it, how the heck do you represent negative numbers in binary?).
>
> I hope this is useful.
>
> On Sat, Apr 14, 2018 at 4:28 PM, Quentin Liu <quentin.liu.0...@gmail.com>
> wrote:
>>
>> Hi all,
>>
>> Suppose I want to multiply two binary numbers whose representation uses
>> lists (e.g. 14 is represented as [1, 1, 1, 0]). Is there any efficient way
>> to do binary multiplication? The way I could come up with involves a lot of
>> intermediate lists that will be discarded eventually and is extremely
>> inefficient. I know one fast algorithm that uses Array but would it be
>> possible to do the multiplication with only lists?
>>
>> Regards,
>> Qingbo Liu
>>
>> _______________________________________________
>> Beginners mailing list
>> Beginners@haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>>
>
>
>
> --
> Steven Leiva
> 305.528.6038
> leiva.ste...@gmail.com
> http://www.linkedin.com/in/stevenleiva
>
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
------------------------------
Message: 4
Date: Wed, 18 Apr 2018 19:07:06 +0000
From: KC <kc1...@gmail.com>
To: Haskell Beginners <beginners@haskell.org>
Subject: Re: [Haskell-beginners] Efficient Binary Multiplication
Message-ID:
<CAMLKXy=a-4longfoyfroggszyhk2m5rpoibweyuqlawfbuc...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi
Must you use only lists?
Must each node only contain one digit?
--
Sent from an expensive device which will be obsolete in a few months
Casey
On Sat, Apr 14, 2018, 1:30 PM Quentin Liu, <quentin.liu.0...@gmail.com>
wrote:
> Hi all,
>
> Suppose I want to multiply two binary numbers whose representation uses
> lists (e.g. 14 is represented as [1, 1, 1, 0]). Is there any efficient way
> to do binary multiplication? The way I could come up with involves a lot of
> intermediate lists that will be discarded eventually and is extremely
> inefficient. I know one fast algorithm that uses Array but would it be
> possible to do the multiplication with only lists?
>
> Regards,
> Qingbo Liu
> _______________________________________________
> Beginners mailing list
> Beginners@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
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