## 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"?

## Comment viewing options

### Looks like a typo to me.

Looks like a typo to me.

### Typos are such a bother in

Typos are such a bother in math papers...

### 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∞.

### 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".