461 reputation
211
bio website cs.bham.ac.uk/~udr
location Birmingham
age
visits member for 2 years, 8 months
seen Jul 18 at 20:41

Professor of Computer Science, with research interests in Programming Languages and Theory of Programming.

My profiles on Theoretical Computer Science, Computer Science, Mathematics, Stackoverflow, and Superuser.

Also on Programmers, where I am shooting for a negative rating (if such a thing is possible)!


Sep
24
awarded  Autobiographer
Apr
7
awarded  Yearling
Feb
18
comment Definition of (projective ?) limit in a presheaf category.
"Projective limit" is their terminology for what is normally called a "limit". Their "inductive limit" is what is normally called a "colimit".
Dec
7
answered lambda calculus and category theory
Dec
7
answered Nice notation for projection maps
Dec
7
comment Good books and lecture notes about category theory.
Eilenberg and Mac Lane's original paper: General theory of natural equivalences says that they defined "category" to define "functor", and "functor" to define "natural transformation". But I get the impression that the category theorists of today don't take that remark all that seriously.
Nov
30
comment When should we take direct limit and when should we take inverse limit?
I think a correction is warranted: The direct limit is not a subset of the union. It is a quotient of the disjoint union.
Nov
30
answered Confused about the definition of a group as a groupoid with one object.
Nov
29
answered What is a (the?) good starting point for learning the modern “higher” mathematics?
Nov
29
answered How can we formalize $\mathrm{Subset}$, the “category” of all subsets?
Nov
15
answered Group identities and inverses
Sep
18
answered Category of Grp is not a subcategory of Set
Aug
9
revised Semidirect Products in category theory?
Added a hyperlink to the online version of Barr/Wells
Aug
9
suggested approved edit on Semidirect Products in category theory?
Aug
7
awarded  Excavator
Aug
7
revised Semidirect Products in category theory?
Corrected the reference to Barr/Wells section number
Aug
7
suggested approved edit on Semidirect Products in category theory?
May
24
revised Analogy for Cosets, Ideals, and Quotient Rings
Another technical typo
May
24
revised Analogy for Cosets, Ideals, and Quotient Rings
Clarified the reference to 'coset'
May
24
revised Analogy for Cosets, Ideals, and Quotient Rings
Corrected a technical typo