I am sorry if this question is not for mathoverflow. I asked the same question in tex stackexchange and got an answer that this question is out of topic. If it's the same here, please let me know.

There are two setbuilder notations, the vertical bar and the colon. In some cases, it is better to make a choice. For example, compare $$\{f \mid f\colon M \rightarrow N \text{ is continuous}\}$$ and $$\{f : f\colon M \rightarrow N \text{ is continuous}\}.$$ Also compare $$\{x : \lvert x \rvert = 1\}$$ and $$\{x \mid \lvert x \rvert = 1\}.$$

Can I use both the vertical bar and the colon in one article to make it more readable? Or should I choose one notation to be consistent?

`$\{(x,y)|x^{2}+y^{2}=1\}$`

instead of`$\{(x,y):x^{2}+y^{2}=1\}$`

. Editors do not like it when papers are filled with negative emoticons. – Joseph Van Name Apr 23 '13 at 15:30