Categories for the working mathematics programmer

[nthiery]

This (series of) patch(es) extends the Sage category framework as a design pattern for organizing generic code.

• Latest version of the patches:

• ​http://combinat.sagemath.org/patches/file/tip/categories-framework-nt.patch (reviewer: David Roe; review essentially complete up to some doctests)
• ​http://combinat.sagemath.org/patches/file/tip/categories-categories-nt.patch (reviewer: Florent Hivert, Javier, David Kohel, Anne Schilling, ...) See CategoriesCategoriesReview
• ​http://combinat.sagemath.org/patches/file/tip/categories-fixsagelib-nt.patch (positive review: Robert Bradshaw) updates to the sage library (import fixes, ...)
• ​http://combinat.sagemath.org/patches/file/tip/categories-fix-combinat-nt.patch (positive review: Florent)
• ​http://combinat.sagemath.org/patches/file/tip/categories-numberfield_homset-nt.patch (reviewer: David)
• ​http://combinat.sagemath.org/patches/file/tip/categories-unpickle_backward_compatibility_aliases-nt.patch (positive review: Florent)

• Status and roadmap: ​http://sagetrac.org/sage_trac/wiki/CategoriesRoadMap

[robertwb]

Where is categories-nt.patch itself?

[nthiery]

Replying to robertwb:

Where is categories-nt.patch itself?

On the sage-combinat patch server. It changes too often to keep it updated on trac. I highlighted the link on top of the description (and improved the ReSTing)

[nthiery]

There are the patches. They are file-orthogonal, so they should apply in any order.

[nthiery]

Note: to get the latest version, please use the patch server.

[was]

NOTES:

(1) Post the latest version here -- I don't want to mess with the patch server.

(2) It says "Experts: please redefine this properly and/or put CC/RR/... in NumberFields?()". I number field is by definition a finite extension of QQ, but CC and RR are infinite extensions of QQ. So we can't put them in that category. Having a function is_NumberFieldHomsetCodomain does seem like a good workaround for now.

(3) The function is_NumberFieldHomsetCodomain in the patch posted here doesn't have any documentation or doctests. Please add them.

(4) I would change these two lines:

        143	        if is_Field(codomain): 
 	144	            return True 

to the single line

        143	        return is_Field(codomain)

which should be functionally the same, and clearer to read.

(5) in a similar spirit, I would change

        145	    except: 
 	146	        pass     
 	147	    return False 

to just

        145	    except: 
 	146	        return False

which is again clearer and equivalent.

(6) I'm puzzled by this in your number_field_rel.py patch:

	543	            return NotImplemented 

What is NotImplemented?? It's not defined in the number_field_rel.py file in sage-4.2.