How to use xparse's NewDocumentCommand for global definition?

Question

This is re: egreg's solution to this question.

Issue:

I would like the \NameOne command to replicate the \NameTwo command where it outputs only when being called on like so: \NameOne. When an argument is being entered into the command: \NameOne{} or \Name{Argument} it prints nothing and is only defining a global definition (as done in \NameTwo).

MWE:

\documentclass{article}
\usepackage{xparse}

\ExplSyntaxOn
\NewDocumentCommand{\NameOne}{g}
 {
  \IfNoValueF{#1}
   {
    \tl_gset:Nn \g_jalep_nameone_tl {#1}
   }
  \tl_use:N \g_jalep_nameone_tl 
 }
\tl_new:N \g_jalep_nameone_tl
\ExplSyntaxOff

\newcommand{\NameTwo}[1]{\xdef\NameTwo{#1}}

\begin{document}
\textbf{NameOne}
\par This should say nothing: \NameOne{Argument}
\par This should say Argument: \NameOne
\par \hrulefill
\par \textbf{NameTwo}
\par This should say nothing: \NameTwo{Argument}
\par This should say Argument: \NameTwo
\end{document}

Output:

Edit:

I realize my question has been previously answered here. If a moderator thinks this question is a repeat, feel free to mark it as such.

you should think really hard before using g option in any distributed code, it breaks all latex syntax guidelines. It is useful in some very special circumstances but should not be used for general latex document commands. — David Carlisle, Jan 15 '19 at 20:03
@DavidCarlisle I will be careful about using this g option. I'm doing all of this for my own curiosity and to better understand the TeX -> LyX relationship, but all in experimentation. @egreg I'm not quite sure I understand? — jed, Jan 15 '19 at 21:35

Skillmon · Accepted Answer · 2019-01-16T11:44:25.480

Just use both possible branches of \IfNoValue (namely \IfNoValueTF):

\documentclass{article}
\usepackage{xparse}

\ExplSyntaxOn
\NewDocumentCommand{\NameOne}{g}
  {
    \IfNoValueTF{#1}
      {
        \tl_use:N \g_jalep_nameone_tl 
      }
      {
        \tl_gset:Nn \g_jalep_nameone_tl {#1}
      }
  }
\tl_new:N \g_jalep_nameone_tl
\ExplSyntaxOff

\newcommand{\NameTwo}[1]{\xdef\NameTwo{#1}}

\begin{document}
\textbf{NameOne}
\par This should say nothing: \NameOne{Argument}
\par This should say Argument: \NameOne
\par \hrulefill
\par \textbf{NameTwo}
\par This should say nothing: \NameTwo{Argument}
\par This should say Argument: \NameTwo
\end{document}

How to use xparse's NewDocumentCommand for global definition?

Issue:

MWE:

Output:

Edit:

1 Answers1