Inserter category
In category theory, a branch of mathematics, the inserter category is a variation of the comma category where the two functors are required to have the same domain category.
Definition
If C and D are two categories and F and G are two functors from C to D, the inserter category Ins(F, G) is the category whose objects are pairs (X, f) where X is an object of C and f is a morphism in D from F(X) to G(X) and whose morphisms from (X, f) to (Y, g) are morphisms h in C from X to Y such that .[1]
Properties
If C and D are locally presentable, F and G are functors from C to D, and either F is cocontinuous or G is continuous; then the inserter category Ins(F, G) is also locally presentable.[2]
gollark: Indeed.
gollark: I mean you're writing more code than necessary for that. More detailed error messages are probably good.
gollark: That... is basically what verbose means?
gollark: This is verbose and loses information, yes.
gollark: I'm not saying C programs will immediately explode and segfault and erase all your data if a file doesn't exist or something. I'm saying that manually propagating error codes, which seems to be the general approach to error handling (outside of just immediately `exit`ing or `longjmp`y things), is verbose and bad.
References
- Seely, R. A. G. (1992). Category Theory 1991: Proceedings of an International Summer Category Theory Meeting, Held June 23-30, 1991. American Mathematical Society. ISBN 0821860186. Retrieved 11 February 2017.
- Adámek, J.; Rosický, J. (10 March 1994). Locally Presentable and Accessible Categories. Cambridge University Press. ISBN 0521422612. Retrieved 11 February 2017.
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