If you are reading this inside of Info in Emacs, you can try out the
multiply-by-seven function by first evaluating the function
definition and then evaluating (multiply-by-seven 3). A copy of
the function definition follows. Place the cursor after the last
parenthesis of the function definition and type C-x C-e. When you
do this, multiply-by-seven will appear in the echo area. (What
this means is that when a function definition is evaluated, the value it
returns is the name of the defined function.) At the same time, this
action installs the function definition.
(defun multiply-by-seven (number) "Multiply NUMBER by seven." (* 7 number))
By evaluating this defun, you have just installed
multiply-by-seven in Emacs. The function is now just as much a
part of Emacs as forward-word or any other editing function you
use. (multiply-by-seven will stay installed until you quit
Emacs. To reload code automatically whenever you start Emacs, see
section Install Code Permanently.)
You can see the effect of installing multiply-by-seven by
evaluating the following sample. Place the cursor after the following
expression and type C-x C-e. The number 21 will appear in the
echo area.
(multiply-by-seven 3)
If you wish, you can read the documentation for the function by typing
C-h f (describe-function) and then the name of the
function, multiply-by-seven. When you do this, a
`*Help*' window will appear on your screen that says:
multiply-by-seven: Multiply NUMBER by seven.
(To return to a single window on your screen, type C-x 1.)
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