Splitting string and retrieving part of it

Question

I would like to take a string in Beamer and retrieve part of it. The solution at How do I split a string? gets me very close to what I want; but using it as example, i.e. if the string is:

\def\MyTeXKnowledge{Not good enough}

How can I retrieve an arbitrary word of this string, e.g. good? The output of the mentioned solution gives (Not)(good)(enough).

Thanks a lot,

Answer 1

\documentclass{article} % or any other

\ExplSyntaxOn

\NewDocumentCommand{\getchunk}{smm}
 {% #1 = optional * (when a command is used for #2
  % #2 = string
  % #3 = item number
  \IfBooleanTF{#1}
   {
    \seq_set_split:NnV \l_tmpa_seq { ~ } #2
   }
   {
    \seq_set_split:Nnn \l_tmpa_seq { ~ } { #2 }
   }
  \seq_item:Nn \l_tmpa_seq { #3 }
 }

\ExplSyntaxOff

\newcommand{\MyTeXKnowledge}{Not good enough}

\begin{document}

\getchunk*{\MyTeXKnowledge}{2}

\getchunk{Not good enough}{3}

\end{document}

We might add a check that there are enough chunks.

\documentclass{article} % or any other
\ExplSyntaxOn
\NewDocumentCommand{\getchunk}{smm}
 {% #1 = optional * (when a command is used for #2
  % #2 = string
  % #3 = item number
  \IfBooleanTF{#1}
   {
    \rigel_getchunk:Vn  #2 { #3 }
   }
   {
    \rigel_getchunk:nn  { #2 } { #3 }
   }
 }
\cs_new_protected:Nn \rigel_getchunk:nn
 {
  \seq_set_split:Nnn \l_tmpa_seq { ~ } { #1 }
  \int_compare:nTF { #2 > \seq_count:N \l_tmpa_seq }
   {
    ??? \ERROR
   }
   {
    \seq_item:Nn \l_tmpa_seq { #2 }
   }
 }
\cs_generate_variant:Nn \rigel_getchunk:nn { V }
\ExplSyntaxOff
\newcommand{\MyTeXKnowledge}{Not good enough}
\begin{document}
\getchunk*{\MyTeXKnowledge}{2}
\getchunk{Not good enough}{3}
\getchunk*{\MyTeXKnowledge}{100}
\end{document}

Also

! Undefined control sequence.
<argument> ???\ERROR

would be raised.

Answer 2

The listofitems package is made to parse lists.

\documentclass{article}
\usepackage{listofitems}
\def\MyTeXKnowledge{Not good enough}
\begin{document}
\setsepchar{ }
\readlist\mylist\MyTeXKnowledge
Second item is: \mylist[2]
The list has \mylistlen{} items.
The last item is: \mylist[-1]
\end{document}