eintr: Conclusion
18 Conclusion
*************
We have now reached the end of this Introduction. You have now learned
enough about programming in Emacs Lisp to set values, to write simple
‘.emacs’ files for yourself and your friends, and write simple
customizations and extensions to Emacs.
This is a place to stop. Or, if you wish, you can now go onward, and
teach yourself.
You have learned some of the basic nuts and bolts of programming.
But only some. There are a great many more brackets and hinges that are
easy to use that we have not touched.
A path you can follow right now lies among the sources to GNU Emacs
and in 
The GNU Emacs Lisp Reference Manual (elisp)Top.
The Emacs Lisp sources are an adventure. When you read the sources
and come across a function or expression that is unfamiliar, you need to
figure out or find out what it does.
Go to the Reference Manual. It is a thorough, complete, and fairly
easy-to-read description of Emacs Lisp. It is written not only for
experts, but for people who know what you know. (The ‘Reference Manual’
comes with the standard GNU Emacs distribution. Like this introduction,
it comes as a Texinfo source file, so you can read it on your computer
and as a typeset, printed book.)
Go to the other built-in help that is part of GNU Emacs: the built-in
documentation for all functions and variables, and ‘find-tag’, the
program that takes you to sources.
Here is an example of how I explore the sources. Because of its
name, ‘simple.el’ is the file I looked at first, a long time ago. As it
happens some of the functions in ‘simple.el’ are complicated, or at
least look complicated at first sight. The ‘open-line’ function, for
example, looks complicated.
You may want to walk through this function slowly, as we did with the
‘forward-sentence’ function. (The ‘forward-sentence’ function
forward-sentence.) Or you may want to skip that function and look at
another, such as ‘split-line’. You don’t need to read all the
functions. According to ‘count-words-in-defun’, the ‘split-line’
function contains 102 words and symbols.
Even though it is short, ‘split-line’ contains expressions we have
not studied: ‘skip-chars-forward’, ‘indent-to’, ‘current-column’ and
‘insert-and-inherit’.
Consider the ‘skip-chars-forward’ function. In GNU Emacs, you can
find out more about ‘skip-chars-forward’ by typing ‘C-h f’
(‘describe-function’) and the name of the function. This gives you the
function documentation.
You may be able to guess what is done by a well named function such
as ‘indent-to’; or you can look it up, too. Incidentally, the
‘describe-function’ function itself is in ‘help.el’; it is one of those
long, but decipherable functions. You can look up ‘describe-function’
using the ‘C-h f’ command!
In this instance, since the code is Lisp, the ‘*Help*’ buffer
contains the name of the library containing the function’s source. You
can put point over the name of the library and press the RET key, which
in this situation is bound to ‘help-follow’, and be taken directly to
the source, in the same way as ‘M-.’ (‘find-tag’).
The definition for ‘describe-function’ illustrates how to customize
the ‘interactive’ expression without using the standard character codes;
and it shows how to create a temporary buffer.
(The ‘indent-to’ function is written in C rather than Emacs Lisp; it
is a built-in function. ‘help-follow’ takes you to its source as does
‘find-tag’, when properly set up.)
You can look at a function’s source using ‘find-tag’, which is bound
to ‘M-.’ Finally, you can find out what the Reference Manual has to say
by visiting the manual in Info, and typing ‘i’ (‘Info-index’) and the
name of the function, or by looking up the function in the index to a
printed copy of the manual.
Similarly, you can find out what is meant by ‘insert-and-inherit’.
Other interesting source files include ‘paragraphs.el’,
‘loaddefs.el’, and ‘loadup.el’. The ‘paragraphs.el’ file includes
short, easily understood functions as well as longer ones. The
‘loaddefs.el’ file contains the many standard autoloads and many
keymaps. I have never looked at it all; only at parts. ‘loadup.el’ is
the file that loads the standard parts of Emacs; it tells you a great
deal about how Emacs is built. (Building Emacs (elisp)Building
Emacs, for more about building.)
As I said, you have learned some nuts and bolts; however, and very
importantly, we have hardly touched major aspects of programming; I have
said nothing about how to sort information, except to use the predefined
‘sort’ function; I have said nothing about how to store information,
except to use variables and lists; I have said nothing about how to
write programs that write programs. These are topics for another, and
different kind of book, a different kind of learning.
What you have done is learn enough for much practical work with GNU
Emacs. What you have done is get started. This is the end of a
beginning.
Info Catalog
eintr: Debugging
eintr: Top
eintr: the-the