Limitations associated with getting length as number

Question

I am representing actual object dimensions with scaled down graphics which capture the relative proportions of the objects (for instance, imagine a simple set of three or four line segments). I would like to annotate the length of a nominal segment on the graphic using that segments actual length. I store the actual lengths using the \newlength and \setlength commands. I apply a suitable scaling factor to these segments by operating on the declared actual lengths in order to compute lengths as they should appear in print. This link provides several possible solutions, e.g.

\newcommand*{\getlength}[2]{%
   % Convert to `cm` and round to two fractional digits:
   \pgfmathsetmacro#1{round(3.51459804*#2)/100.0}%
}

When I provide a value of 180 cm

\newlength{\lengtha}
\setlength{\lengtha}{180cm}
\getlength{\annotlengtha}{\lengtha}

I encounter some restriction, that is, I receive a Dimension too large error message. Might someone explain the limitations associated with this approach?

A recent answer with relevant info http://tex.stackexchange.com/questions/125617/plotting-a-parabola-dimension-too-large-message — percusse, Jul 29 '13 at 20:46
Since you have some responses below that seem to answer your question, please consider marking one of them as ‘Accepted’ by clicking on the tickmark below their vote count (see How do you accept an answer?). This shows which answer helped you most, and it assigns reputation points to the author of the answer (and to you!). It's part of this site's idea to identify good questions and answers through upvotes and acceptance of answers. — samcarter_is_at_topanswers.xyz, Feb 03 '18 at 20:42

score 2 · Accepted Answer · edited Apr 13 '17 at 12:35

2

Somewhere on this site, Dividing dimensions to get a count, percusse explained how egreg taught him (and now me) to turn lengths into dimensionless numbers using "count" variable types. One can assign a length to the count, and it turns it into a large integer (representing the length in TeX internal units).

Then, you can divide two counts to get a dimensionless ratio, for example. A size of 180cm poses no problem for this technique.

\documentclass{article}
\usepackage{fp}
\begin{document}
\newcount\mycounta
\newcount\mycountb
\newlength{\lengtha}
\setlength{\lengtha}{180cm}
\newlength{\lengthb}
\setlength{\lengthb}{30cm}
\mycounta=\lengtha
\mycountb=\lengthb
\the\mycounta~\the\mycountb

\FPdiv\result{\the\mycounta}{\the\mycountb}
\result

\end{document}

enter image description here

edited Apr 13 '17 at 12:35

Community

1

answered Jul 31 '13 at 11:51

Steven B. Segletes

237,551

Maybe this http://tex.stackexchange.com/questions/85717/dividing-dimensions-to-get-a-count/85724#85724 ;) – percusse Jul 31 '13 at 11:54
@percusse Mea culpa. I will revise to give credit. – Steven B. Segletes Jul 31 '13 at 11:56
Oh no, give the credit to egreg not to the question please :p – percusse Jul 31 '13 at 11:57
@percusse, the citation train is getting pretty long 8^) – Steven B. Segletes Jul 31 '13 at 12:02
Indeed, but he explained it to me in chat so I had to use that disclaimer :) – percusse Jul 31 '13 at 12:05

Limitations associated with getting length as number

1 Answers1