# Extract first letter of each word in a sentence

I don't know if already exists a question like this, but after 20 minutes I haven't found one.

There are similar ones, like How to define a command that bolds the first letter of each word in the input argument?, but it's not the same as mine.

I'm looking for a command \shortenthis{…} which extracts the first letter of each word in the command. \shortenthis{Leonard Euler} will give us LE. In case of \shortenthis{Pierre de Fermat} it should give PdF.

The idea is to shorten names.

I guess this is “easy” with LaTeX3 (although I'm a newbie, I looked in the documentation, and examples in this site, and couldn't do it), but any solution would be accepted.

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Already found an answer. If someone marks this as a duplicate, will delete it. If not, may be it's good for the community to have it here. – Manuel Mar 1 '14 at 12:15
Which question do you think this is a duplicate of? – egreg Mar 1 '14 at 12:16
I don't know, but my memory keeps saying that I have already seen something like this. – Manuel Mar 1 '14 at 12:16
Why don't you use some acronym facility instead of re-inventing things? – Harish Kumar Mar 1 '14 at 12:17
I have an answer ready, shoot if you still need it. :) – Paulo Cereda Mar 1 '14 at 12:20

Almost a copy of cgnieder's solution in the link I posted.

\documentclass{scrartcl}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand\shortenthis{ m }
{
\shorten_this:n { #1 }
}

\seq_new:N \l_shorten_seq
\cs_new_protected:Npn \shorten_this:n #1
{
\seq_set_split:Nnn \l_shorten_seq { ~ } { #1 }
\seq_map_inline:Nn \l_shorten_seq
{
}
}

\ExplSyntaxOff
\begin{document}
\shortenthis{Pierre de Fermat}
\shortenthis{Leonard Euler}
\end{document}

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In this answer, the macro \getargsC extracts each word of the argument into the macros \argi, \argii, etc. Then I set up a loop to grab the first letter of each word with a simple \def

\documentclass{article}
\usepackage{ifthen}
\newcounter{index}\setcounter{index}{0}
\def\firstletters#1{%
\getargsC{#1}%
\whiledo{\theindex<\narg}{%
\stepcounter{index}%
\edef\nextword{\csname arg\romannumeral\theindex\endcsname}%
\expandafter\getfirst\nextword\relax%
}%
}
\def\getfirst#1#2\relax{#1}
\begin{document}
\firstletters{This is a test of the Emergency Broadcast System.}
\end{document}


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