multiply-by-seven, An Overview
Both the use of the special form
interactive and one way to
display a value in the echo area can be illustrated by creating an
interactive version of
Here is the code:
(defun multiply-by-seven (number) ; Interactive version. "Multiply NUMBER by seven." (interactive "p") (message "The result is %d" (* 7 number)))
You can install this code by placing your cursor after it and typing C-x C-e. The name of the function will appear in your echo area. Then, you can use this code by typing C-u and a number and then typing M-x multiply-by-seven and pressing RET. The phrase ‘The result is …’ followed by the product will appear in the echo area.
Speaking more generally, you invoke a function like this in either of two ways:
Both the examples just mentioned work identically to move point forward
three sentences. (Since
multiply-by-seven is not bound to a key,
it could not be used as an example of key binding.)
(See Some Keybindings, to learn how to bind a command to a key.)
A prefix argument is passed to an interactive function by typing the META key followed by a number, for example, M-3 M-e, or by typing C-u and then a number, for example, C-u 3 M-e (if you type C-u without a number, it defaults to 4).