Reddit alien in LaTeX

What to do on a lazy sunday afternoon? Well, there are probably a thousand useful
things one could do, but I chose to do something completely useless. And here it is, the reddit alien drawn in LaTeX (using PsTricks) :)

\documentclass{memoir}

\usepackage{pstricks}
\usepackage{pst-all}

\begin{document}

\thispagestyle{empty}

%\psset{linecolor=red}
\psset{linewidth=1pt}
\begin{pspicture}(6,9)
%\psgrid[subgriddiv=1,griddots=10,gridlabels=10pt](0,0)(12,12)
\psframe(0,0)(6,9)
% head
\psellipse(3,6)(1.8,1)
% ears
\psarc{-}(1.5,6.5){0.4}{38}{230}
\psarc{-}(4.5,6.5){0.4}{-50}{142}
% eyes
\pscircle[fillstyle=solid,linestyle=none,fillcolor=orange](2.3,6.3){0.3}
\pscircle[fillstyle=solid,linestyle=none,fillcolor=orange](3.7,6.3){0.3}
% mouth
\psbezier(2.3,5.6)(2.5,5.3)(3.5,5.3)(3.7,5.6)
% the tentacle thingie
\psline(2.99,6.99)(3.6,8)
\psline(3.581,7.993)(4.1,7.8)
\pscircle(4.35,7.65){0.3}
% arms
\psarc{-}(2.8,4.3){1.1}{130}{231}
\psarc{-}(3.15,4.3){1.1}{-48}{50}
% body
\psbezier(2.1,5.15)(2.0,4.7)(1.8,3.3)(2.6,2.7)
\psbezier(3.85,5.15)(4.1,4.65)(4.1,3.3)(3.4,2.7)
% feet
\psline(1.65,2.7)(4.3,2.7)
\psarc{-}(2.1,2.685){0.45}{70}{180}
\psarc{-}(3.85,2.685){0.45}{0}{105}
\end{pspicture}

\end{document}

Note that I used the memoir document class, but you could also use article if you don't have memoir available (the results would be the same). The alien does not look exactly the same as the official reddit one, but who cares? And here is what you should get when you run this example through LaTeX:

And people say LaTeX suxx...

Deferred printing in LaTeX

Ever written a textbook? Ever written any document that has questions/problems and answers to those problems? Usually when you do this, you want to have questions printed in one place (or questions in each section of the document), and answers printed at the end of the document (so your readers, which are usually students, would try to actually solve the problem rather than just look at the solution which is right under the problem).
Now, I don't know how most of you usually do this, but up until now the only way I knew to do this is the "brute force" approach---I would simply write the questions and then, at the end of the document, I would write the answers. The obvious drawback of this approach is that you have to look up each individual question when writing the answers (just to see what it was) and this can quickly become very boring. Or, if you have the questions/answers on paper, they are usually written in pairs question/answer so you have to first type all the questions (ignoring the answers), and then go back to the begining of the paper and type all the answers (ignoring the questions). Anyway, I hope you get the picture why I hate doing this.
Wouldn't it be great if I could somehow have the question and its answer in the same place in the source of the document (notice that we are not talking about WYSIWYG text processors here), but then defer the printing of answers in the output document (that is, print the answers at the end of the document)? The solution to my problem comes in a form of the LaTeX box mechanism. Just take a look at this minimal example:

\documentclass{article}

\newbox\answerscollect
\newcounter{problem}
\setcounter{problem}{0}
\renewcommand{\theproblem}{\textit{Problem \arabic{problem}.}\,}

\def\answer#1{\par\setbox\answerscollect=\vbox{\unvbox\answerscollect\vspace{5mm}\theproblem\,#1\par}}
\def\printanswers{\unvbox\answerscollect\setbox\answerscollect=\vbox{}}
\def\initbox{\setbox\answerscollect=\vbox{Answers:\par}}

\newcommand{\problem}[1]{\addtocounter{problem}{1}\par\theproblem\textit{#1}}

\begin{document}

\initbox

\section{Intro}
Some text before...

\problem{What is the capital of the US?}
\answer{Washington, D.~C.}

\problem{What is 2+2?}
\answer{4}

\section{Foo}

Some other text goes here...

\section{Answers}

\printanswers

\end{document}

Now I know it looks a bit complicated, but it really isn't. What we are doing is creating a box and storing all the answers in it, and then, when the time is write, we simply print all the contents of that box using the \printanswers command. This way, we can simply have the problem and its solution (answer) in the same place in the source of the document, but have the answers appear in a totally different place in the output pdf (or postscript or whatever). Now, I'm not going to go into details of the LaTeX code itself here. Those who know LaTeX will pretty much understand the code, and those who don't should first learn the basics before trying to get this. Anyway, the code can be used out-of-the-box; if someone would like to change something but doesn't know how, you can contact me. Last, but not least, here is how the output pdf looks like:


UPDATE: As Evan noted, if you are going to use multiple files, don't use \include. Instead, use the \input command which does not create new .aux files.

How to insert watermark in LaTeX

For my first post this year, I'll start off with something a bit different. This time we'll take a look at how to insert a watermark in a document using LaTeX. Note here that by watermark I mean some text that will appear on the background of each page of the document.
As with everything else in the wonderful world of LaTeX, there are more ways to do this. I know of two, which I will write about here. The first one is fairly simple, just include the package draftcopy and voila. Here's a minimal example of how it works:

\documentclass{article}
\usepackage{draftcopy}

\title{Lorem ipsum}

\begin{document}
\maketitle

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

\end{document}

Running the previous example through LaTeX gives the following output:

Note that running pdflatex on this example will NOT insert the watermark. I use LaTeX->dvi->ps->pdf route to obtain the pdf.
Of course the draftcopy package gives a lot of options to customize the watermark, of which I believe \draftcopyName is the most useful. If you want the word ENTWURF to be printed instead of DRAFT, which is used by default, you would add the line "\draftcopyName{ENTWURF}{155}" in the preamble. The number 155 is the scaling factor for the font---play around with it to get the scaling you want.
For those that like to do it the hard way (like me:) ), here is a piece of code that does pretty much the same thing:

          \AddToShipoutPicture{%
            \setlength{\@tempdimb}{.5\paperwidth}%
            \setlength{\@tempdimc}{.5\paperheight}%
            \setlength{\unitlength}{1pt}%
            \put(\strip@pt\@tempdimb,\strip@pt\@tempdimc){%
        \makebox(600,-700){\rotatebox{45}{\textcolor[gray]{0.75}%
        {\fontsize{6cm}{6cm}\selectfont{DRAFT}}}}%
            }%
        }

To use this code, you have to include the following packages: graphicx, eso-pic, and type1cm. Here is a minimal example:

\documentclass{article}

\usepackage{graphicx}
\usepackage{type1cm}
\usepackage{eso-pic}
\usepackage{color}

\makeatletter
\AddToShipoutPicture{%
            \setlength{\@tempdimb}{.5\paperwidth}%
            \setlength{\@tempdimc}{.5\paperheight}%
            \setlength{\unitlength}{1pt}%
            \put(\strip@pt\@tempdimb,\strip@pt\@tempdimc){%
        \makebox(0,0){\rotatebox{45}{\textcolor[gray]{0.75}%
        {\fontsize{6cm}{6cm}\selectfont{DRAFT}}}}%
            }%
}
\makeatother

\title{Lorem ipsum}

\begin{document}
\maketitle

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

\end{document}

Be sure not to forget the \makeatletter and \makeatother commands. Unlike with draftcopy, running pdflatex on this example WILL insert the watermark in the pdf. I find this code nice because I can directly tinker with the various options. For example, if I want to change the angle of the text, I'll change the number inside the \rotatebox, if I want to move the text around the page, I'll change the two numbers inside \makebox, if I want to change the grayscale, I'll change the number inside \textcolor, etc.
UPDATE: The above code, as Ivijay pointed out, puts the word DRAFT on every page of the document. If you want it to appear on only one, you should use the

AddToShipoutPicture*

instead of

AddToShipoutPicture

. This command only adds the watermark to one page (first one if you leave the watermark code in your preamble).

UPDATE: Neno wants to know how to use a picture instead of text. Well, it's just a matter of replacing the lines

\makebox(0,0){\rotatebox{45}{\textcolor[gray]{0.75}%
{\fontsize{6cm}{6cm}\selectfont{DRAFT}}}}%

with something like

\includegraphics{image.eps}

Of course, you might have to play around with adjusting the width and height of the picture, depending on its size. Also, you might want to change tempdimb and tempdimc to properly position the image.

UPDATE: hcr suggests using draftwatermark package to do this sort of thing. I've just had a look at the package, and using it really seems simple. For most of the things I did here, there is a nice command that does that. However, some things are missing from the package. First, the color of the text is always grey (you can choose the grey scale, but can't have the watermark text in, say, red. There does not seem to be a way to change the typeface of the font for the watermark text, and the text is always centered, you can't move it around. And finally, there is no way you could insert a picture as a watermark (which is what Neno wanted to do), and IMHO this could be a big issue for many people who may want their company's logo as a watermark. So anyway, draftwatermark is a great choice if you just want to insert a word (centered) in the background of each page. If you need anything more sophisticated than that, you will have to do something in the line of what I described here.

UPDATE: Amy wants to know is there a way to put the watermark only on some pages, preferably using something like \begin{watermark} and \end{watermark}. Well, Amy, there is no easy solution to your problem. One thing you could do is use \AddToShipoutPicture* that places the watermark only on one page, and then paste the code wherever you need it. Of course, this is ugly. I have managed to hack together some solution that seems to work, but the code is really ugly and I don't advise anyone to use it unless you really need to :). So, here goes:

\documentclass{article}

\usepackage{graphicx}
\usepackage{type1cm}
\usepackage{eso-pic}
\usepackage{color}
\usepackage{everypage}

\newenvironment{water}{\AddEverypageHook{\waterb}}{\AddThispageHook{\waterb}\AddEverypageHook{\watere}}

\makeatletter
\newcommand{\waterb}{
\AddToShipoutPicture*{%
            \setlength{\@tempdimb}{.5\paperwidth}%
            \setlength{\@tempdimc}{.5\paperheight}%
            \setlength{\unitlength}{1pt}%
            \put(\strip@pt\@tempdimb,\strip@pt\@tempdimc){%
        \makebox(0,0){\rotatebox{45}{\textcolor[gray]{0.75}%
        {\fontsize{6cm}{6cm}\selectfont{DRAFT}}}}%
            }%
}}
\makeatother

\makeatletter
\newcommand{\watere}{
\AddToShipoutPicture*{%
            \setlength{\@tempdimb}{.5\paperwidth}%
            \setlength{\@tempdimc}{.5\paperheight}%
            \setlength{\unitlength}{1pt}%
            \put(\strip@pt\@tempdimb,\strip@pt\@tempdimc){%
        \makebox(0,0){\rotatebox{45}{\textcolor[gray]{1}%
        {\fontsize{6cm}{6cm}\selectfont{DRAFT}}}}%
            }%
}}
\makeatother

\title{Lorem ipsum}

\begin{document}

page one

\newpage

\begin{water}
 First watermarked page
 \newpage
 Second watermarked page
 \newpage
 Third watermarked page
\end{water}

\newpage

This page should not be watermarked
\end{document}

Well, Amy, let me know if this works for you...