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.)