Info Catalog eintr: Cutting & Storing Text eintr: zap-to-char

eintr: Storing Text

 
 Storing Text in a List
 ======================
 
 When text is cut out of a buffer, it is stored on a list.  Successive
 pieces of text are stored on the list successively, so the list might
 look like this:
 
      ("a piece of text" "previous piece")
 
 The function ‘cons’ can be used to create a new list from a piece of
 text (an “atom”, to use the jargon) and an existing list, like this:
 
      (cons "another piece"
            '("a piece of text" "previous piece"))
 
 If you evaluate this expression, a list of three elements will appear in
 the echo area:
 
      ("another piece" "a piece of text" "previous piece")
 
    With the ‘car’ and ‘nthcdr’ functions, you can retrieve whichever
 piece of text you want.  For example, in the following code, ‘nthcdr 1
 ...’ returns the list with the first item removed; and the ‘car’ returns
 the first element of that remainder—the second element of the original
 list:
 
      (car (nthcdr 1 '("another piece"
                       "a piece of text"
                       "previous piece")))
           ⇒ "a piece of text"
 
    The actual functions in Emacs are more complex than this, of course.
 The code for cutting and retrieving text has to be written so that Emacs
 can figure out which element in the list you want—the first, second,
 third, or whatever.  In addition, when you get to the end of the list,
 Emacs should give you the first element of the list, rather than nothing
 at all.
 
    The list that holds the pieces of text is called the “kill ring”.
 This chapter leads up to a description of the kill ring and how it is
 used by first tracing how the ‘zap-to-char’ function works.  This
 function calls a function that invokes a function that manipulates the
 kill ring.  Thus, before reaching the mountains, we climb the foothills.
 
    A subsequent chapter describes how text that is cut from the buffer
 is retrieved.  Yanking Text Back Yanking.
 

Info Catalog eintr: Cutting & Storing Text eintr: zap-to-char