LaTeX is a typesetting program that produces excellently typeset documents.

Typesetting is placing text onto a page with all the style formatting

defined, so that content looks as intended. It is extensively used for

producing high quality scientific and mathematical documents. It may also be

used for producing other kinds of documents, ranging from simple one page

articles to complete books. LaTeX is based on the TeX typesetting language.

LaTeX is pronounced either as "Lah-tech" or "Lay-tech". 

Why LaTeX?

~~~~~~~~~~

A few reasons for using LaTeX - 

  * It produces documents with excellent visual quality.

  * It does the typesetting for you, leaving you - the author - to focus on

    writing the content. You will appreciate this, as you learn more.

  * It makes writing math just as easy as writing simple text.

  * It's renowned for it's stability and a virtually bug free code base.

  * It is light on your resources as compared to most of the word processors

    available today.

  * It uses plain text files as input and can give output in a variety of

    formats including PDFs and html making it platform independent.

  * It is free software (free as in freedom) and gratis too.

  * It is widely used and has a large user community.

Course Outline

~~~~~~~~~~~~~~

In this course, we will learn enough LaTeX to be a able to produce a simple

document with text, tables, figures, math, references and bibliography. We

will also briefly see how to create presentations using LaTeX, such as the

one use for the slides of this course.

The sample document, ``sample.pdf``, available in the course material, will

serve as a teaching/learning tool to learn LaTeX. During the course, we shall

reproduce this sample document, starting from scratch, in LaTeX

+++++++++++++++++++++++++++++

A look at the sample document gives us an idea about the various elements

present in the document, that we will be learning during this course.

We shall be learning how to add the following elements to our LaTeX

documents.

  * Sections & Subsections

  * Appendices

LaTeX is not a Word Processor

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

What do we mean by LaTeX not being a Word Processor? Suppose we wanted to

create a simple document as shown in the image below. If one used a normal

word processor, the author would have to worry about setting the font sizes

of the fonts, centering the title, date and author information, etc.

.. image:: images/latex_not_wp.png

   :alt: LaTeX is not a Word Processor

To generate this document in LaTeX, we just tell it what we want as the

title, author's name, date etc. and what we want as the content. LaTeX takes

care of proper font size ratios and other presentation details.

::

  \documentclass{article}

  \title{My First Document}

  \author{FOSSEE}

  \date{January 2011}

  \begin{document}

     \maketitle

     Hello world!

  \end{document}

LaTeX can be considered to be a document based markup language. What we mean

by a markup language is that you mark up pieces of your text to be particular

elements of your document and then a typesetter or processor typesets your

document based on a set of rules. What do we mean by being document-based? It

means, that in LaTeX, you can change the structure of the whole document

consistently, with a few changes in the preamble of the document, with-out

having to change each element separately.

First steps -- Typesetting a minimal document

---------------------------------------------

Let us start with a minimal example to learn how to write a LaTeX document

and compile it to see the **typeset** output.

To begin, type out the following code into your text editor and save it as

``draft.tex``. ::

To compile your document, type the following command in your terminal::

  $ pdflatex draft.tex

Note: The ``latex`` command is often used, instead of ``pdflatex`` to get the

``dvi`` output. But, throughout this course, we shall use ``pdflatex`` to

compile our documents.

What does it mean?

~~~~~~~~~~~~~~~~~~

As we have already seen, LaTeX is a document based markup. The first line,

``\documentclass{article}``, tells that our document is an article type

document. LaTeX then, typesets the document accordingly. The documentclass

command, defines the structure and formatting of our document.

The ``begin`` and ``end`` document commands, mark the beginning and the end

of the content of the LaTeX document. The text in between the begin and end

commands is typeset in the output document. 

A little digression

~~~~~~~~~~~~~~~~~~~

Just like in ``bash`` and ``Python``, the commands in LaTeX are

case-sensitive. ``\Documentclass`` is therefore not a valid command. 

All the commands in LaTeX begin with a ``\``. An environment begins with a

``begin`` command and ends with an ``end`` command. In our minimal example,

``document`` is an environment. Only the text enclosed by the begin and end

commands is effected by the environment. 

So, as expected LaTeX ignores anything that is written after the

``\end{document}`` command. (The part of the file before the

``\begin{document}`` command is called the preamble, and is used to

*"configure"* the LaTeX typesetter and change various parameters for

typesetting. Details later.)

Essentially, anything written after the ``\end{document}`` command turns out

to be a comment. But, how do we write comments with in the document. ``%`` is

the character to indicate comments. Anything written after a ``%`` symbol in

a line, is ignored. For example, we can add a comment to the minimal document

saying, this is our first document in LaTeX, by saying ``% My First LaTeX

document``. 

But what if we wanted to insert the ``%`` symbol in the document? We can do

so by escaping it with a ``\`` (backslash). ``%`` is one of the many special

characters in LaTeX. The others are, ``~ # $ ^ & _ { } \``. All of them,

except the ``\`` itself, can be inserted by escaping it with a ``\``. To

insert a ``\`` in our document, we use the command ``\textbackslash``. 

What would happen if we escape a ``\`` with a ``\``? Yes, you guessed it. A

double backslash is actually another command. It inserts a new line in the

typeset document. The ``\\`` command or ``\newline`` command is used to

insert a newline in the output document. Line breaks in the input document,

do not translate into line breaks in the output document. A single line break

in the input document, doesn't cause any change in the output. A single empty

line causes a change in paragraphs in the output. (Multiple empty lines are

equivalent to a single empty line.) Similarly, multiple spaces are treated as

a single space. 

Adding Structure

----------------

Let us now, look at giving the document some basic structure, like title,

sections, etc. 

~~~~~~~~~~~~~~~~~~

As we have already seen, the ``documentclass`` command tells LaTeX, the type

of the document that we intend to create. Some of the available LaTeX classes

are, ``article``, ``proc``, ``report``, ``book``, ``slides``, ``letter``.

Each class has a few differences in how the content of the document is

typeset.

The ``documentclass`` command also accepts a few optional parameters. For

example::

  \documentclass[12pt,a4paper,oneside,draft]{report}

``12pt`` specifies the size of the main font in the document. The relative

sizes of the various fonts is maintained, when the font size is changed. If

no size is specified, ``10pt`` is assumed by default.

``a4paper`` specifies the size of the paper to be used for the document.

``draft`` marks the hyphenation and justification problems in the document

with a small square in the right hand margin of the document, so that they

can be easily spotted.

``\begin{document}`` directive. We compile the document to see if the details

appear in the document, but they donot. These details do not appear in the

document until we use the ``\maketitle`` command with the document

environment to instruct LaTeX to place the top matter information into the

document. Now the document has these details, on compiling again.

Next we shall add an abstract to our document. LaTeX provides an environment,

for adding an abstract to the document. 

::

The abstract environment is placed at the location where we wish it to appear

in the document.

Now let's look at how to add (chapters,) sections and sub-sections to our

document. Let's add the section headings and sub headings present in our

sample document to the working copy of our document.

If the document was a longer document, we could have used a report or a book

class. (Note: Books donot have the abstract environment.) Let's look at what

happens to the document, when we change it to the report class.

The numbering strangely begins from zero, now. This is because, chapters have

an additional sectioning command called ``\chapter``. The chapter is one

level above a section and since, our document does not have a ``\chapter``

command, the sections are numbered from 0. To change this, we add a chapter

command before the first section. We say

::

Now, observe that we now have a chapter title appearing and the numbering

starting from 1.

controlled by a variable called the secnumdepth. By default it is set to 2.

We can now, change it to 3 and get numbering for subsubsections also. 

::

What do you expect to happen if we changed the secnumdepth to 1? What if it

is 0 or -1?

Our sample document is not long enough to warrant a table of contents, but

let us learn to add a table of contents to a LaTeX document. If you ever

tried adding a table of contents, to a document in a wordprocessor, you would

know how much of a trouble it is. In LaTeX, it is a matter of just one

command and placing the command at the location where you would want to have

the table of contents. Let's now add a table of contents to our draft. Now,

compile the document and look at the output document. It does not have the

table of contents!

On the first compilation only the "Contents" heading appears in the document,

but the actual table does not appear. You will need to compile your document

once more, for the actual table to appear in your document. On the first run,

LaTeX has gone through your document and generated a temporary file

(``.toc``), with the entries that should go into the table of contents. These

entries are made, when you compile your document for the second time.

Note that any section/block that has been numbered automatically appears in

the table of contents. It is possible to get un-numbered sections, for

instance a Preface or a Foreword section to appear in the Table of Contents.

Let's change our Introduction section to be an un-numbered one and try to

make it appear in the table-of-contents. ::

We shall talk about adding and managing bibliographies, later in the course.

Now, that we have the basic structure of the document, let's get into the

content and the details of it.

Let's begin with adding the second paragraph to the introduction section.

Let's place the text of the second para, after the first line, that we

already have. Now, compile the document.

As already discussed, we need to an insert an empty line, to insert a new

paragraph in LaTeX. Also, notice that the new paragraph is indented.

Look at the quotation marks around the text, Sigh Pie. They are not formatted

properly. To place quotation marks in LaTeX, you should use ````` character

for the left quote & ``'`` character for the right quote. For double quotes,

they should be used twice.

The names of the software tools, Scilab, Matlab, etc. appear in italics or

emphasized as it is called in LaTeX. To emphasize text, the ``\emph`` command

is used.

Let's also add the contents of the subsection "Sub-packages of Scipy". We

shall add the table as plain text, until we learn how to edit tables.

Let's try and form a tabular structure by separating the left and right

columns using spaces. On compiling we find that LaTeX doesn't add multiple

spaces between words. Just like multiple empty lines, multiple spaces are

considered as a single space.

Also, we notice that ``LaTeX`` starts a new paragraph at the beginning of the

table. To avoid this, we use the ``flushleft`` environment.

The names of the sub-packages appear in a fixed width font in the sample

document provided to us. The headings of the columns appear in bold-face.

Let's make changes to this effect.

``\textbf`` is used to change text to bold face and ``\texttt`` is used to

change text to fixed width font.

We could also change the separating - (hyphen) to an em-dash (or en-dash) --

is em-dash and --- is an em-dash, to improve the appearance of the document.

The section on Use of Scipy in this course, contains lists. Let's now add

lists to our document. The ``enumerate`` environment adds numbered lists to

our document and the ``itemize`` environment adds un-numbered lists.

``\item`` command adds a new entry to a list. Note, that LaTeX can easily

handle nested lists. In fact most environments can be embedded within other

environments, without any problems.

LaTeX also has a description list, which shall be an exercise, for you.

Let's now add the footnote to pylab. LaTeX provides a footnote command to add

a footnote.

We added the footnote with Appendix A, as plain text. But, in case we added

another Appendix before the section on using ``pylab``, the footnote will

have to be edited. To avoid this, LaTeX provides a handy system of labels and

referencing.