[texhax] detect characters in strings

[Brandon Kuczenski]

Philip Taylor (Webmaster, Ret'd) wrote:
 > Maybe Brandon can pick something useful out of this :
 >
 > \documentclass {minimal}
 >
 > \def \head #1e#2\relax {#1}
 > \def \mantissa #1{\head #1e\relax}
 >
 > \begin {document}
 >     \mantissa {0.00346}\par
 >     \mantissa {3.46e-03}\par
 > \end {document}

That's remarkable- it will definitely assist my effort.  Thanks!

Uwe Lueck wrote:
> 
> Somewhere earlier I wrote that the macros from substr.sty are not expandable. This really means that they break in an \edef as well as in a \typeout, sorry. And BTW, a pair of braces seems to be missing with the first \typeout ... and what are you doing with #1 in \SciToFP? Please tell what you expect \SciToFP to do ...
> 
> Cheers, 
> 
>     Uwe.
> 
> 

Apologies!  I do not really understand plain TeX yet (at least I finally 
bought the TeXbook about a month ago).  It is a peculiar language.. I 
love the fact that there are macros called, e.g., \the.

Here's a bit of background.  Recently, through this list, I learned 
about \arrayjob[x] and, in combination with fixed point math in fp.sty 
it has revolutionized my use of TeX-- I'm now migrating to PStricks for 
all my data visualization.  (I once used Matlab, but due to 
circumstances lately I'm trapped in excel.)

I made a simple command to extract array data into a macro which is
fp-friendly (i.e. trimmed whitespace):

\usepackage{arrayjobx,fp,trimspaces}
\def\trimspace#1{\trim at spaces@in{#1}}

\def\ArraytoFP#1{\trimspace\cachedata\FPclip#1\cachedata}

Usage would be:
\checkMyArray(index1,...)\ArraytoFP\myarrayvalue

Now I'm modifying that to respond to the presence of scientific
notation:

\usepackage{substr}

\def\ArrayStoFP#1{\trimspace\cachedata%
\IfCharInString{e}{\cachedata}{\SciToFP#1\cachedata}{\FPclip#1\cachedata}}

So \SciToFP would assign to #1 a macro that expands to the fixed-point 
version of \cachedata.

My task now is to extract exponent, convert it into a 1 and a decimal 
point with the proper number of zeros between them, and \FPmul by the 
mantissa.  Philip's comments look helpful, as well as the code of 
substr, coolstr, etc.  I still don't understand how I may use \loop to 
accomplish this, though.  But that's ok- I'm on a tight deadline so I'm 
going to have to wait until later to finish that puzzle.

-Brandon