[OS X TeX] using lengths inside pictures

[Alex Scorpan]

>  \begin{picture}(12,3)
>  \put(2,1+\mylength){Hello!}
> \end{picture}

\put needs plain numbers as its arguments in parentheses.  Not  
arithmetic, and certainly not lengths (that have units, like cm).

The quick and very crappy way that I know for feeding some arithmetic  
into {picture} is to highjack the {calc} package.

I'd actually be very interested to hear from the TeXperts on how to  
do this better and more elegantly.  Anyways, my crappy hack is that I  
write something like

	\usepackage{calc}

	\newcounter{gaga}
	\newcounter{gugu}
	....

	\setcounter{gaga}{\value{gugu}+1}

	\put(2,\thegaga){...

If there's any recursion tricks you're trying to implement there, it  
starts to get iffy.  I use

	\edef\n{\thegaga}
	\put(2,\n){...

to force the evaluation of gaga at that precise moment.  And, of  
course, any sort of recurrent self-call starts to be beautified by  
\expandafter's...  the horror...

---

My experience with {picture} tells me that, if it can at all be  
avoided, it is just simpler and better to do all computations off- 
TeX.  If you need to rescale your whole picture, use

	\setlength{\unitlength}{<something else than 1pt>}

before the {picture} env.  Or, when more is needed, abuse the  
{graphicx} package, and do things like

	\rotatebox{45}{\begin{picture}(10,10) .... \end{picture}}

	\scalebox{.4}[.5]{\begin{picture}(10,10) ... \end{picture}}

Notice that (unlike acting on \unitlegth) \scalebox is also going to  
thiken/thin your line widths.

---

Ah, and, of course, general advice for using {picture}:  If you plan  
to output to pdf or ps, do add
	
	\usepackage{pict2e}

at the beginning of your doc.  It helps with many things, by  
unloading some of the work on pdf or ps.


Alex

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