Info Catalog eintr: Interactive eintr: multiply-by-seven in detail

eintr: Interactive multiply-by-seven

 
 An Interactive ‘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 ‘multiply-by-seven’.
 
    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:
 
   1. By typing a prefix argument that contains the number to be passed,
      and then typing ‘M-x’ and the name of the function, as with ‘C-u 3
      M-x forward-sentence’; or,
 
   2. By typing whatever key or keychord the function is bound to, as
      with ‘C-u 3 M-e’.
 
 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.)
 
    (Some Keybindings 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).
 

Info Catalog eintr: Interactive eintr: multiply-by-seven in detail