Ceci est une ancienne révision du document !
Defining a new log-like function in LaTeX
Use the \mathop command, as in:
\newcommand{\diag}{\mathop{\mathrm{diag}}}
Subscripts and superscripts on \diag will be placed below and
above the function name, as they are on \lim.
If you want your subscripts and superscripts always placed to the right, do:
\newcommand{\diag}{\mathop{\mathrm{diag}}\nolimits}
The amsmath bundle (in its amsopn package, which is automatically
loaded by amsmath) provides a command \DeclareMathOperator
that takes does the same job as the first definition above.
To create our original \diag command, one would say:
\DeclareMathOperator{\diag}{diag}
\DeclareMathOperator* declares the operator always to have its
sub- and superscripts in the
« “\limits” position ».
The amsopn command \operatorname allows you to introduce ad hoc operators
into your mathematics, so \[ \operatorname{foo}(bar) \] typesets the same as
\DeclareMathOperator{\foo}{foo} ... \[ \foo(bar) \]
As with \DeclareMathOperator there's a starred version
\operatorname* for sub- and superscripts in the limits position.
(It should be noted that “log-like” was reportedly a joke on Lamport's part; it is of course clear what was meant.)
