Is there a multiple function composition operator? [duplicate]

Solution 1:

If I were writing something in which I had to do a large number of these, the following is probably not quite what I would do: $$ \mathop{\bigcirc}^n_{k=0} f_k \quad \text{ or } \quad \mathop{\bigcirc}^0_{k=n} f_k \ . $$ Instead, I'd go over to tex.stackexchange.com and ask how to make this thing look respectable instead of like a workaround. I'd probably want it to be comparable in size and boldness to something like $\displaystyle\bigcap$ in $\displaystyle\bigcap_{k=0}^n A_k$ or to $\displaystyle\bigoplus$. Before the \begin{document} I'd put

\newcommand{\Circ}{blah blah blah}

with a capital C distinguishing it from \circ).