Updated solution using the features of etoolbox which has essentially implemented the “\MapCommand” and named it \forcsvlist

\documentclass{article} \usepackage{amsmath} \usepackage{etoolbox} \newcommand{\DeclareMyOperator}[1]{% \expandafter\DeclareMathOperator\csname #1\endcsname{#1} } \newcommand{\DeclareMathOperators}{\forcsvlist{\DeclareMyOperator}} \DeclareMathOperators{Rep,Tet,Maps,Diff} \begin{document} Operators: $\Rep, \Tet, \Maps, \Diff$ \end{document} 

“For historical reasons”, I leave my original answer bellow.

Combining the previous answers from Grigory and Andrew I was able to come up with the following somewhat cleaner implementation which also exposes a nice user interface.

\documentclass{article} \usepackage{amsmath} \makeatletter \def\ops@declare#1{% \expandafter\DeclareMathOperator\csname #1\endcsname{#1} } \def\ops@scan#1,{% \ifx#1\relax \let\ops@next\relax \else \ops@declare{#1}\let\ops@next\ops@scan \fi\ops@next } \newcommand{\DeclareMathOperators}[1]{\ops@scan#1,\relax,} \makeatother \DeclareMathOperators{Rep,Tet,Maps,Diff} \begin{document} Operators: $\Rep, \Tet, \Maps, \Diff$ \end{document} 

Updated solution using the features of etoolbox which has essentially implemented the “\MapCommand” and named it \forcsvlist

\documentclass{article} \usepackage{amsmath} \usepackage{etoolbox} \newcommand{\DeclareMyOperator}[1]{% \expandafter\DeclareMathOperator\csname #1\endcsname{#1} } \newcommand{\DeclareMathOperators}{\forcsvlist{\DeclareMyOperator}} \DeclareMathOperators{Rep,Tet,Maps,Diff} \begin{document} Operators: $\Rep, \Tet, \Maps, \Diff$ \end{document} 

“For historical reasons”, I leave my original answer bellow.

Combining the previous answers from Grigory and Andrew I was able to come up with the following somewhat cleaner implementation which also exposes a nice user interface.

\documentclass{article} \usepackage{amsmath} \makeatletter \def\ops@declare#1{% \expandafter\DeclareMathOperator\csname #1\endcsname{#1} } \def\ops@scan#1,{% \ifx#1\relax \let\ops@next\relax \else \ops@declare{#1}\let\ops@next\ops@scan \fi\ops@next } \newcommand{\DeclareMathOperators}[1]{\ops@scan#1,\relax,} \makeatother \DeclareMathOperators{Rep,Tet,Maps,Diff} \begin{document} Operators: $\Rep, \Tet, \Maps, \Diff$ \end{document} 

Combining the previous answers from Grigory and Andrew I was able to come up with the following somewhat cleaner implementation which also exposes a nice user interface.

\documentclass{article} \usepackage{amsmath} \makeatletter \def\ops@declare#1{% \expandafter\DeclareMathOperator\csname #1\endcsname{#1} } \def\ops@scan#1,{% \ifx#1\relax \let\ops@next\relax \else \ops@declare{#1}\let\ops@next\ops@scan \fi\ops@next } \newcommand{\DeclareMathOperators}[1]{\ops@scan#1,\relax,} \makeatother \DeclareMathOperators{Rep,Tet,Maps,Diff} \begin{document} Operators: $\Rep, \Tet, \Maps, \Diff$ \end{document} 

Updated solution using the features of etoolbox which has essentially implemented the “\MapCommand” and named it \forcsvlist

\documentclass{article} \usepackage{amsmath} \usepackage{etoolbox} \newcommand{\DeclareMyOperator}[1]{% \expandafter\DeclareMathOperator\csname #1\endcsname{#1} } \newcommand{\DeclareMathOperators}{\forcsvlist{\DeclareMyOperator}} \DeclareMathOperators{Rep,Tet,Maps,Diff} \begin{document} Operators: $\Rep, \Tet, \Maps, \Diff$ \end{document} 

“For historical reasons”, I leave my original answer bellow.

Combining the previous answers from Grigory and Andrew I was able to come up with the following somewhat cleaner implementation which also exposes a nice user interface.

\documentclass{article} \usepackage{amsmath} \makeatletter \def\ops@declare#1{% \expandafter\DeclareMathOperator\csname #1\endcsname{#1} } \def\ops@scan#1,{% \ifx#1\relax \let\ops@next\relax \else \ops@declare{#1}\let\ops@next\ops@scan \fi\ops@next } \newcommand{\DeclareMathOperators}[1]{\ops@scan#1,\relax,} \makeatother \DeclareMathOperators{Rep,Tet,Maps,Diff} \begin{document} Operators: $\Rep, \Tet, \Maps, \Diff$ \end{document}