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Review
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   In the last few chapters we have introduced a fair number of
functions and special forms.  Here they are described in brief, along
with a few similar functions that have not been mentioned yet.

`eval-last-sexp'
     Evaluate the last symbolic expression before the current location
     of point.  The value is printed in the echo area unless the
     function is invoked with an argument; in that case, the output is
     printed in the current buffer.  This command is normally bound to
     `C-x C-e'.

`defun'
     Define function.  This special form has up to five parts: the name,
     a template for the arguments that will be passed to the function,
     documentation, an optional interactive declaration, and the body
     of the definition.

     For example:

          (defun back-to-indentation ()
            "Move point to first visible character on line."
            (interactive)
            (beginning-of-line 1)
            (skip-chars-forward " \t"))

`interactive'
     Declare to the interpreter that the function can be used
     interactively.  This special form may be followed by a string with
     one or more parts that pass the information to the arguments of the
     function, in sequence.  These parts may also tell the interpreter
     to prompt for information.  Parts of the string are separated by
     newlines, `\n'.

     Common code characters are:

    `b'
          The name of an existing buffer.

    `f'
          The name of an existing file.

    `p'
          The numeric prefix argument.  (Note that this `p' is lower
          case.)

    `r'
          Point and the mark, as two numeric arguments, smallest first.
          This is the only code letter that specifies two successive
          arguments rather than one.

     Note: Code Characters for `interactive',
     for a complete list of code characters.

`let'
     Declare that a list of variables is for use within the body of the
     `let' and give them an initial value, either `nil' or a specified
     value; then evaluate the rest of the expressions in the body of
     the `let' and return the value of the last one.  Inside the body
     of the `let', the Lisp interpreter does not see the values of the
     variables of the same names that are bound outside of the `let'.

     For example,

          (let ((foo (buffer-name))
                (bar (buffer-size)))
            (message
             "This buffer is %s and has %d characters."
             foo bar))

`save-excursion'
     Record the values of point and mark and the current buffer before
     evaluating the body of this special form.  Restore the values of
     point and mark and buffer afterward.

     For example,

          (message "We are %d characters into this buffer."
                   (- (point)
                      (save-excursion
                        (goto-char (point-min)) (point))))

`if'
     Evaluate the first argument to the function; if it is true,
     evaluate the second argument; else evaluate the third argument, if
     there is one.

     The `if' special form is called a "conditional".  There are other
     conditionals in Emacs Lisp, but `if' is perhaps the most commonly
     used.

     For example,

          (if (string-equal
               (number-to-string 21)
               (substring (emacs-version) 10 12))
              (message "This is version 21 Emacs")
            (message "This is not version 21 Emacs"))

`equal'
`eq'
     Test whether two objects are the same.  `equal' uses one meaning
     of the word `same' and `eq' uses another:  `equal' returns true if
     the two objects have a similar structure and contents, such as two
     copies of the same book.  On the other hand, `eq', returns true if
     both arguments are actually the same object.

`<'
`>'
`<='
`>='
     The `<' function tests whether its first argument is smaller than
     its second argument.  A corresponding function, `>', tests whether
     the first argument is greater than the second.  Likewise, `<='
     tests whether the first argument is less than or equal to the
     second and `>=' tests whether the first argument is greater than
     or equal to the second.  In all cases, both arguments must be
     numbers or markers (markers indicate positions in buffers).

`string<'
`string-lessp'
`string='
`string-equal'
     The `string-lessp' function tests whether its first argument is
     smaller than the second argument.  A shorter, alternative name for
     the same function (a `defalias') is `string<'.

     The arguments to `string-lessp' must be strings or symbols; the
     ordering is lexicographic, so case is significant.  The print
     names of symbols are used instead of the symbols themselves.

     An empty string, `""', a string with no characters in it, is
     smaller than any string of characters.

     `string-equal' provides the corresponding test for equality.  Its
     shorter, alternative name is `string='.  There are no string test
     functions that correspond to >, `>=', or `<='.

`message'
     Print a message in the echo area. The first argument is a string
     that can contain `%s', `%d', or `%c' to print the value of
     arguments that follow the string.  The argument used by `%s' must
     be a string or a symbol; the argument used by `%d' must be a
     number.  The argument used by `%c' must be an ascii code number;
     it will be printed as the character with that ASCII code.

`setq'
`set'
     The `setq' function sets the value of its first argument to the
     value of the second argument.  The first argument is automatically
     quoted by `setq'.  It does the same for succeeding pairs of
     arguments.  Another function, `set', takes only two arguments and
     evaluates both of them before setting the value returned by its
     first argument to the value returned by its second argument.

`buffer-name'
     Without an argument, return the name of the buffer, as a string.

`buffer-file-name'
     Without an argument, return the name of the file the buffer is
     visiting.

`current-buffer'
     Return the buffer in which Emacs is active; it may not be the
     buffer that is visible on the screen.

`other-buffer'
     Return the most recently selected buffer (other than the buffer
     passed to `other-buffer' as an argument and other than the current
     buffer).

`switch-to-buffer'
     Select a buffer for Emacs to be active in and display it in the
     current window so users can look at it.  Usually bound to `C-x b'.

`set-buffer'
     Switch Emacs' attention to a buffer on which programs will run.
     Don't alter what the window is showing.

`buffer-size'
     Return the number of characters in the current buffer.

`point'
     Return the value of the current position of the cursor, as an
     integer counting the number of characters from the beginning of the
     buffer.

`point-min'
     Return the minimum permissible value of point in the current
     buffer.  This is 1, unless narrowing is in effect.

`point-max'
     Return the value of the maximum permissible value of point in the
     current buffer.  This is the end of the buffer, unless narrowing
     is in effect.