Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Darij Grinberg
Hi Nathann,

You are right. Infinite words don't belong into an algebra; you cannot
multiply them. Barring hack reasons, the change is correct.

  Best regards,
  Darij

On Sun, Jan 5, 2014 at 3:32 PM, Nathann Cohen nathann.co...@gmail.com wrote:
 Or possibly : you know that your algebras can break at any moment if you
 play with the wrong words, but you want to be able to define this anyway
 when you know what you are doing ?...

 Nathann


 On Sunday, January 5, 2014 3:30:40 PM UTC+1, Nathann Cohen wrote:

 Hello everybody !!

 Because of broken doctests in #12867, I find myself opening the file
 sage/categories/examples/algebras_with_basis.py, and about to do something
 potentially  big.

 I am about to remplace this
 CombinatorialFreeModule.__init__(self, R, Words(alphabet), category =
 AlgebrasWithBasis(R))

 By this:
 CombinatorialFreeModule.__init__(self, R, Words(alphabet, infinite=False),
 category = AlgebrasWithBasis(R))

 And I would like to know what you think of it. Because I wondered : can
 you really define (in Sage) an algebra over (Finite+Infinite) Words, given
 that you cannot even check whether two infinite words are ... equal ?

 This is my problem. And if there is no reason to create (in Sage) an
 algebra over infiinite words, my problem is settled :-P

 Tell me what you think !

 Nathann

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Nathann Cohen


 You are right. Infinite words don't belong into an algebra; you cannot 
 multiply them. Barring hack reasons, the change is correct. 


HMmm... And what do you think of Shuffle Algebras on infinite words ? Is 
this one correct or not ?

It looks okay to me.. But if you tell me that it is not for yet another 
reason it will make my debugging *much* easier :-P

Nathann 

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Nathann Cohen
Okay, I just created an element manually instead of calling an_element().

Nathann


On 5 January 2014 15:59, Nathann Cohen nathann.co...@gmail.com wrote:

 You are right. Infinite words don't belong into an algebra; you cannot
 multiply them. Barring hack reasons, the change is correct.


 HMmm... And what do you think of Shuffle Algebras on infinite words ? Is
 this one correct or not ?

 It looks okay to me.. But if you tell me that it is not for yet another
 reason it will make my debugging *much* easier :-P

 Nathann

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Darij Grinberg
Oops, I've just realized that you *can* multiply infinite words,
though I'm not sure if this has ever been used. (No, you cannot take
their shuffle product.)

On Sun, Jan 5, 2014 at 4:29 PM, Nathann Cohen nathann.co...@gmail.com wrote:
 Okay, I just created an element manually instead of calling an_element().

 Nathann


 On 5 January 2014 15:59, Nathann Cohen nathann.co...@gmail.com wrote:

 You are right. Infinite words don't belong into an algebra; you cannot
 multiply them. Barring hack reasons, the change is correct.


 HMmm... And what do you think of Shuffle Algebras on infinite words ? Is
 this one correct or not ?

 It looks okay to me.. But if you tell me that it is not for yet another
 reason it will make my debugging *much* easier :-P

 Nathann

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Vincent Delecroix
How do you define multiplication ?! If it is concatenation then uv = u...

2014/1/5, Darij Grinberg darijgrinb...@gmail.com:
 Oops, I've just realized that you *can* multiply infinite words,
 though I'm not sure if this has ever been used. (No, you cannot take
 their shuffle product.)

 On Sun, Jan 5, 2014 at 4:29 PM, Nathann Cohen nathann.co...@gmail.com
 wrote:
 Okay, I just created an element manually instead of calling an_element().

 Nathann


 On 5 January 2014 15:59, Nathann Cohen nathann.co...@gmail.com wrote:

 You are right. Infinite words don't belong into an algebra; you cannot
 multiply them. Barring hack reasons, the change is correct.


 HMmm... And what do you think of Shuffle Algebras on infinite words ? Is
 this one correct or not ?

 It looks okay to me.. But if you tell me that it is not for yet another
 reason it will make my debugging *much* easier :-P

 Nathann

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Darij Grinberg
On Sun, Jan 5, 2014 at 5:54 PM, Vincent Delecroix
20100.delecr...@gmail.com wrote:
 How do you define multiplication ?! If it is concatenation then uv = u...

Yes, but it's associative, so it works... (Except I don't expect it to
have much of a use.)

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Christian Stump

 Yes, but it's associative, so it works... (Except I don't expect it to
 have much of a use.)


can you be more specific? How is the product uv defined? I see that you
have a shuffle product defined, but I don't see that you have
concatenation...

Thanks, Christian

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Nathann Cohen
H... I just had Nicolas on the phone who told me that both can be
changed to finite words only. Aand he had Florent around to
confirm.

I also think that the concatenation product is not well defined. And I
actually wrote that in the patch already :-/

On the other hand I did not touch the Shuffle Product.

Well, tell me what you think ^^;

Nathann


On 5 January 2014 19:09, Darij Grinberg darijgrinb...@gmail.com wrote:

 Huh? I thought shuffle does not work (because ... sh ... would
 be a sum of infinitely many identical words), but uv is well-defined
 (and equals u when u is infinite)?

 On Sun, Jan 5, 2014 at 7:08 PM, Christian Stump
 christian.st...@gmail.com wrote:
  Yes, but it's associative, so it works... (Except I don't expect it to
  have much of a use.)
 
 
  can you be more specific? How is the product uv defined? I see that you
 have
  a shuffle product defined, but I don't see that you have concatenation...
 
  Thanks, Christian
 
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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Vincent Delecroix
Concatenation product is well defined but not well implemented in
Sage. If u is infinite then uv = u for any (finite or infinite) word
v. It is not a free monoid anymore.

That being said, you can build the algebra on finite words, the one on
infinite words (which is really stupid) and the one on all words. I
guess only the first one matters.

The shuffle algebra is not well defined on infinite words (the product
becomes an infinite sum). So please turn infinite=False in both
situations.

Vincent

2014/1/5, Nathann Cohen nathann.co...@gmail.com:
 H... I just had Nicolas on the phone who told me that both can be
 changed to finite words only. Aand he had Florent around to
 confirm.

 I also think that the concatenation product is not well defined. And I
 actually wrote that in the patch already :-/

 On the other hand I did not touch the Shuffle Product.

 Well, tell me what you think ^^;

 Nathann


 On 5 January 2014 19:09, Darij Grinberg darijgrinb...@gmail.com wrote:

 Huh? I thought shuffle does not work (because ... sh ... would
 be a sum of infinitely many identical words), but uv is well-defined
 (and equals u when u is infinite)?

 On Sun, Jan 5, 2014 at 7:08 PM, Christian Stump
 christian.st...@gmail.com wrote:
  Yes, but it's associative, so it works... (Except I don't expect it to
  have much of a use.)
 
 
  can you be more specific? How is the product uv defined? I see that you
 have
  a shuffle product defined, but I don't see that you have
  concatenation...
 
  Thanks, Christian
 
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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Nathann Cohen
 The shuffle algebra is not well defined on infinite words (the product
 becomes an infinite sum). So please turn infinite=False in both
 situations.

Okay... So I will edit #12867 again :-P

Nathann

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Nathann Cohen
I just edited ticket #12867. Thank you for your help :-)

Nathann

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Re: [sage-combinat-devel] Re: About Free Algebras, infinite Words and equality

2014-01-05 Thread Vincent Delecroix
Thank you for your work !!

2014/1/5, Nathann Cohen nathann.co...@gmail.com:
 I just edited ticket #12867. Thank you for your help :-)

 Nathann

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