# \StrMid and \MakeUppercase problem

What's wrong with this:

\documentclass{minimal}
\usepackage{xstring}
\begin{document}
\newcommand{\cim}{c1095}
\StrMid{\MakeUppercase{\cim}}{1}{1}
\StrMid{\cim}{2}{100}
\end{document}


\MakeUppercase{\cim} works but \StrMid{\MakeUppercase{\cim}}{1}{1} doesn't work. Why?

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Perhaps try \MakeUppercase{\noexpand\StrMid{\cim}{1}{1}}? Not sure the \noexpand is needed, and I can't test on this computer. –  Bruno Le Floch Jan 16 '12 at 18:45

Since you don't need to uppercase the string beforehand, this is a way:

\StrMid{\cim}{1}{1}[\temp]
\expandafter\MakeUppercase\expandafter{\temp}


We store the extracted string in a temporary macro and then apply \MakeUppercase to the result.

If strings are formed by "safe" characters (printable ASCII characters), the simpler \uppercase can be used:

\StrMid{\cim}{1}{1}[\temp]\uppercase\expandafter{\temp}

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Thanks, that works –  balping Nov 6 '11 at 14:00

The xstring package carries out an \edef (exhaustive expansion) on its argument. Stefan has suggested on approach, but depending on what you want to achieve an alternative is to create an expandable version of the upper case command. There is one built-in to expl3, which needs renaming for use in a document:

\documentclass{article}
\usepackage{xstring,expl3}
\ExplSyntaxOn
\let\MakeExpandableUppercase\tl_expandable_uppercase:n
\ExplSyntaxOff
\begin{document}
\newcommand{\cim}{c1095}
\StrMid{\MakeExpandableUppercase{\cim}}{1}{1}\space or
\StrMid{\expandafter\MakeExpandableUppercase\expandafter{\cim}}{1}{1} ?
\StrMid{\cim}{2}{100}
\end{document}


As I've indicated, I'm not sure what order you want the case change to happen in, relative to the string extraction.

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