Talk:F-algebra

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[edit] 1 + X

What does "1 + X" in the example mean? I (not a category theorist) assume it's the set of numbers y such that y = 1 + x for some x in X. But that only makes sense if X is a set of numbers (or I guess any ring with 1). That doesn't seem to extend very well to the entire category of sets. Staecker 02:11, 25 July 2006 (UTC)

I'm not a category theorist either, but I'm guessing it refers to the disjoint union. That is, X + Y is the union of the sets X and Y, but with the elements "relabelled" to make sure the sets don't overlap. See category of sets and coproduct to see how this idea fits into category theory.

I believe the article is wrong when it says "where 1 is some singleton subset of X". If we are indeed talking about the disjoint union then 1 can refer to any singleton set. GilesEdkins 00:22, 21 January 2007 (UTC)

I've clarified the notations of the example. I hope that they are clear now. Samuel Mimram 17:56, 22 January 2007 (UTC)

Thanks- should've known it was a coproduct. Staecker 19:32, 22 January 2007 (UTC)