Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural

2014-05-13 Thread Andrei Popescu
. Andrei On Tue, 5/13/14, Lawrence Paulson wrote: Subject: Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural To: "Andrei Popescu" Cc: "isabelle-dev@mailbroy.informatik.tu-muenchen.de" Date: Tuesday, M

Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural

2014-05-13 Thread Jasmin Christian Blanchette
Am 13.05.2014 um 14:11 schrieb Manuel Eberl : > In particular, any algebraic datatype with only one constructor can be > rewritten into a corresponding codatatype, allowing you to use primcorec for > it. In fact, even (nonrecursive) datatypes with several constructors can be rewritten into a c

Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural

2014-05-13 Thread Manuel Eberl
Yes, but the underlying reason for that is that complex numbers are isomorphic to pairs of real numbers, and binary product types are "degenerate" (I would rather say very basic) co-algebraic datatypes. So my point (and I would guess Andrei's as well) is that this really has nothing to do with com

Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural

2014-05-13 Thread Lawrence Paulson
it’s not just about syntactic sugar. It seems to me that the complex numbers are an elegant (if degenerative) example of a co-algebraic datatype. The co-recursive definitions look absolutely natural to me. Larry On 11 May 2014, at 12:55, Andrei Popescu wrote: > The fact that one can use primco

Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural

2014-05-13 Thread Johannes Hölzl
Am Sonntag, den 11.05.2014, 04:55 -0700 schrieb Andrei Popescu: > > Johannes wrote: > > Theorems about complex numbers are now stated only using Re and Im, > the Complex > > constructor is not used anymore. It is possible to use primcorec to > defined the behaviour of a complex-valued function. >

Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural

2014-05-11 Thread Andrei Popescu
> Johannes wrote: > Theorems about complex numbers are now stated only using Re and Im, the > Complex >  constructor is not used anymore. It is possible to use primcorec to defined >the behaviour of a complex-valued function. >> Makarius wrote: >> That is indeed very nice.  Is that a new invent

Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural Re/Im view

2014-05-10 Thread Manuel Eberl
Hallo, I stumbled across this just now and thought about it for a bit. I don't know much about category theory, but I would say the intuitive “reason” why complex numbers can be represented this way is the following: 1. ℂ is a field extension of ℝ with degree 2 (since it is constructed from the ℝ

Re: [isabelle-dev] NEWS: avoid the Complex constructor, use the more natural Re/Im view

2014-05-07 Thread Makarius
On Wed, 7 May 2014, Johannes Hölzl wrote: * Theorems about complex numbers are now stated only using Re and Im, the Complex constructor is not used anymore. It is possible to use primcorec to defined the behaviour of a complex-valued function. This is also a surprising application of primcor

[isabelle-dev] NEWS: avoid the Complex constructor, use the more natural Re/Im view

2014-05-07 Thread Johannes Hölzl
* Theorems about complex numbers are now stated only using Re and Im, the Complex constructor is not used anymore. It is possible to use primcorec to defined the behaviour of a complex-valued function. Removed theorems about the Complex constructor from the simpset, they are available as