Math Mode – Define Additional Math Operators to be Typeset in Roman

Question

Mathematical operators, such as function names, should be set in roman type, not italics. Latex already has commands for some operators, including \max, \min, and \log. How can I define additional such commands?

Answer 1

\DeclareMathOperator{\foo}{foo} and \DeclareMathOperator*{\hocolim}{hocolim} for sub- and superscripts in the limits position.

This requires

\usepackage{amsmath}

which is recommended for math documents anyway.

Minimal example:

\documentclass{article}
\usepackage{amsmath}

\DeclareMathOperator{\foo}{foo}
\DeclareMathOperator*{\hocolim}{hocolim}

\begin{document}

Example of $\foo(x)$ and $\foo x$.

Example of $\hocolim_{x\in X} f(x)$ and displayed
\begin{equation*}
\hocolim_{x\in X} f(x)
\end{equation*}

\end{document}