TeX/let
Synopsis
edit\let<new-command>[[<spaces>]=]<original-command>
Description
edit\let
allows you to copy the content of a command into a new command.
Unlike making a macro that calls the original command, \let
allows you to subsequently modify the old command while still retaining its functionality under the new command. It is often used to change the behaviour of an existing command (but not replace it entirely). In such cases \renewcommand
may fail, and \let
may be required.
The equal sign (and the spaces before it) are not required, but may be useful in some special cases where the second argument is a space or a equal sign.
Examples
editIf one wanted to change the behaviour of a command \foo
wherever it was called, such that \bar
were executed first, the following may seem appropriate.
\renewcommand{\foo}{\bar\foo}
This, however, will create a recursive loop where calling \foo
will repeatedly call itself until the computer's memory is exhausted.
In order to change the behaviour of \foo
to include some other behaviour, the \let
command is used:
\let\originalfoo\foo
\renewcommand{\foo}{\bar\originalfoo}
The first line copies the contents of the \foo
command into the new command \originalfoo
. The second line modifies the \foo
command to execute \bar
followed by the original contents of the \foo
command (which are now stored in \originalfoo
).