First letter upper case and other letters in lower case

Question

I'm trying to make uppercase the first letter in string and lowercase other letters. Example: Input:eXample String and output Example string. How can I do that?

Answer 1

\documentclass{article}
\newcommand\capmystring[1]{\capmystringaux#1\relax}
\def\capmystringaux#1#2\relax{\uppercase{#1}\lowercase{#2}}
\begin{document}
eXample String

\capmystring{eXample String}
\end{document}

In this case, \capmystring sends the argument to an auxiliary routine with an attached \relax token appended at the end. The auxiliary routine reads two arguments up to the \relax (one would hope and assume that the argument itself contains no \relax tokens). The way TeX absorbs arguments, the argument #1 will be a single token, whereas #2 will be all the remaining tokens up to (but not including) the originally supplied \relax. At that point it is as simple as applying \uppercase to the first token stored in #1, and \lowercase to the remaining tokens, all of which are stored in #2.

Answer 2

The expl3 language can do this using Unicode data:

\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewExpandableDocumentCommand \firstcap { m } { \text_titlecase:n {#1} }
\ExplSyntaxOff
\begin{document}
eXample String

\firstcap{eXample String}
\end{document}

(assuming a new enough LaTeX2e format; for older cases, add \usepackage[utf8]{inputenc} with pdfTeX.)

We might extend this approach to allow for language-specific case mappings

\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\NewExpandableDocumentCommand \firstcap { O{} m }
  { \text_titlecase:nn {#1} {#2} }
\ExplSyntaxOff
\begin{document}
\firstcap{IJSSELMEER}     % Ijsselmeer
\firstcap[nl]{IJSSELMEER} % IJsselmeer
\end{document}

Answer 3

Another solution using the stringstrings package:

\documentclass{article}

\usepackage{stringstrings}
\newcommand{\firstcap}[1]{\caselower[e]{#1}\capitalize{\thestring}}

\begin{document}
eXample String

\firstcap{eXample String}
\end{document}

Explanation: \caselower makes the whole string lowercase, the option [e] saves the result in \thestring such that it can be further processed, finally \capitalize does what it says and outputs the result.

Answer 4

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Here's a LuaLaTeX-based solution that works with all UTF8-encoded characters. This approach can handle UTF8-encoded characters because it uses -- in place of the "standard" Lua string functions string.gsub, string.upper, and string.lower -- the functions unicode.utf8.gsub, unicode.utf8.upper, and unicode.utf8.lower. These functions are provided by the unicode.utf8 library, which is loade automatically by LuaTeX.

% !TeX program = lualatex
\documentclass{article}
\usepackage{luacode}
\begin{luacode}
function first_cap ( s )
   s = unicode.utf8.gsub ( s , "(%a)(%a*)", function(x,y)
          return ( unicode.utf8.upper(x) .. unicode.utf8.lower(y) )
          end )
   tex.sprint ( s )
end
\end{luacode}
\newcommand{\firstcap}[1]{\directlua{first_cap(\luastring{#1})}}

\begin{document}
\firstcap{eXample String}

\firstcap{Once upOn A tIMe i saw a BAT.}

\firstcap{ä ö ü é à è ł óÓÓÓ żĄĄĄ }
\end{document}

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Addendum -- I just realized that I may have misinterpreted the OP's requirements: I had assumed that the uppercasing of the first letter in a word should apply to every word in the argument of \firstcap, not just the very first word. To make the uppercasing operation apply to the first word only (and thus applying the lowercasing operation to all other words in the argument of \firstcap), simply change the second argument of the Lua function unicode.utf8.gsub from "(%a)(%a*)" to "(%a)(.*)".