LaTeX中\newcommand, \renewcommand, \providecommand的用法
\newcommand defines a new command, and makes an error if it is already defined.
\renewcommand redefines a predefined command, and makes an error if it is not yet defined.
\providecommand defines a new command if it isn't already defined, or does nothing if it exists.
If you want to define a command whether it is new or predefined, you can use \def or
- \providecommand \foo{}
- \renewcommand \foo{…}