In TeX how can I define a list of data such that I can use a numerical argument to call for one entry out of the list

Question

I would like to be able to have a defined macro something like this:

\def\testmacro[1]{[54.7],[74.1],[98.5]}

Such that when I call

\testmacro{2},

in a document,

74.1

is printed. Is this possible?

Background:

I'm writing a C++ program that will export data to a TeX file. I have up to twenty items (but sometimes fewer), which have various measurement, like pressure. This TeX file will call for a template, which will specify how different data is actually printed. In the template, I will specify that I want to print pressure for the second item here.

I'd love to be able to say:

\def\pressure1{54.7}
\def\pressure2{74.1}

etc, but Tex can't handle numbers in macro names. Any suggestions?

Thanks, Ben

Look here https://tex.stackexchange.com/questions/159118/how-to-iterate-over-a-comma-separated-list — sergiokapone, Aug 07 '17 at 22:08
@sergiokapone Iterating over items of a list isn't quite the same as accessing particular items. For a more general solution: How to implement (low-level) arrays in TeX. — Alan Munn, Aug 07 '17 at 22:14

score 5 · Accepted Answer · answered Aug 07 '17 at 22:10

5

You can have numbers in command names, you just need to access them indirectly or via non-standard catcodes.

\newcount\zcount
\def\pressure{\afterassignment\zpressure\zcount}
\def\zpressure{\csname\string\pressure\the\zcount\endcsname}
\def\zdef#1#2#{\expandafter\def\csname\string#1#2\endcsname}

\zdef\pressure1{54.7}
\zdef\pressure2{74.1}
\zdef\pressure3{98.5}



Pressure 2 is \pressure2.

\bye

answered Aug 07 '17 at 22:10

David Carlisle

757,742

Thanks! This seems to do exactly what I want. I'm going to play with it a bit - I actually have a bunch of fields for each item (start pressure, end pressure, 02 percentage, etc) so - if I understand correctly - it looks like I'll have to duplicate lines two and three for each field. Thank you! This was extremely helpful, and it probably would have taken me a year or two - if I was lucky - to figure it out on my own.
Best Regards,

Ben
– Ben McCandless Aug 08 '17 at 02:32
@BenMcCandless you can do whatever you would do if you used a,b,c instead of 1,2,3, either separate macros \pressure1{10} and \temperature1{25.6} or have one macro with two fields stuff1{{10}{25.6}} – David Carlisle Aug 08 '17 at 06:49

sergiokapone · Answer 2 · 2017-08-07T23:02:17.850

2

My solution based on Kpym's answer

    \documentclass[varwidth,border=7]{standalone}
    \usepackage{pgfmath}
    \begin{document}

    \def\pressureData{{1.2, 3.3, 2.3 ,3.4}}
    \def\pressure#1{\pgfmathparse{\pressureData[#1]}\pgfmathresult}

    \pressure0

    \pressure1

    \pressure2

    \pressure3      

    \end{document}

edited Aug 07 '17 at 23:02

answered Aug 07 '17 at 22:56

sergiokapone

5,578
1
16
39

How would you add a data item the way the OP proposes (namely, \def\pressure314{3.14})? – jarnosc Aug 08 '17 at 00:29
Thank you! In my case, being able to add items after the initial declaration is a plus, but this is a great answer for situations where the entire selection of items can be defined at once. I'll definitely remember this for later. – Ben McCandless Aug 08 '17 at 02:27

In TeX how can I define a list of data such that I can use a numerical argument to call for one entry out of the list

2 Answers2