Home » forums » LtU Forum

Obscure question about a remark in "A Tutorial on (Co)Algebras and (Co)Induction".

This is kind of obscure. In the "A Tutorial on (Co)Algebras and (Co)Induction" we find the remark (page 28):

If A has more than two elements, then conc(x, y) /= conc(y, x), because they give rise to different observations...

Why is it "more than two" instead of "two or more"?

By Jason Dusek at 2009-05-13 13:29 | LtU Forum | previous forum topic | next forum topic | other blogs | 4599 reads

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Looks like a typo to me.

Looks like a typo to me.

By Leon P Smith at Wed, 2009-05-13 14:03 | login or register to post comments

Typos are such a bother in

Typos are such a bother in math papers...

By Jason Dusek at Thu, 2009-05-14 11:18 | login or register to post comments

Still correct...

It is true that, for domain A with two or more elements, the concatenation function conc : A∞ x A∞ → A∞ will not be commutative.

But, logically, that implies domain that, for A with more than two elements, conc will not be concatenative. Thus, the statement was correct, just not as broad as it could have been.

It seems pointless to me to pick on non-pivotal correct points when there are no doubt plenty of pivotal but incorrect ones to pick on in various documents! ^_^

I must say I find rather odd the representation of a 'list' as A∞.

By dmbarbour at Wed, 2009-05-13 16:56 | login or register to post comments

Point taken...

But I still think it's a typo. ;-) I imagine that it's a unintended mash-up of both "more than one element" and "two or more elements".

By Leon P Smith at Wed, 2009-05-13 22:37 | login or register to post comments