How to replace single hyphen with other text such as double hyphen?

Question

I want to replace - with --. I am able to replace \\ with -- using the following code:

{\def \\ {--\ } #3}

but if I try:

{\def - {--\ } #3} %Option 1
{\def- {--\ } #3} %Option 2
{\def-{--\ } #3} %Option 3
{\def - {{--\ }} #3} %Option 4

or any combination of the above, it causes

Missing control sequence inserted.
<inserted text>
                \inaccessible
    l.77         \begin
                   {rItemize}

in the part of the .tex file:

    \begin{rESubsection}
        {text}
        {text}
        {\def \\ {--\ }{Start Date \\ End Date}}
        \begin{rItemize} % here
            \item text
        \end{rItemize}
    \end{rESubsection}

ChatGPT did not help even if it gave a running code. I tried all above code on different compilers versions of pdflatex (2022, 2021, 2020) but to no avail.

Here is a full minimal working .tex file on pdflatex compiler version 2020 (legacy) on overleaf as per comments request.

\documentclass[11pt,letterpaper]{article} % Font size and paper type

\usepackage[parfill]{parskip} % Remove paragraph indentation

\usepackage{xparse} % used for any mmooo...

\usepackage{enumitem} % For rItemize left margin
\usepackage[left=0.4 in,top=0.4in,right=0.4 in,bottom=0.4in]{geometry} % Document margins
%\usepackage[margin=0.4in]{geometry}

\NewDocumentEnvironment{rSubsection}{mmmo}{
  \textbf{#1}, {#2}\IfValueT{#4}{, \textit{#4}}. \hfill {\def \\ {--\ } #3}
  \par
}{}

\NewDocumentEnvironment{rItemize}{
    \begin{itemize}
      \raggedright
}{
  \end{itemize}
}

\begin{document}
%----------------------------------------------------------------------------------------
% Professional Experience   
%----------------------------------------------------------------------------------------

    \begin{rSubsection}
        {Role}
        {Company Name}
        {Date - Date}
        [Location]
        \begin{rItemize}
            \item Text.
        \end{rItemize}

            \begin{rSubsection}
        {Role}
        {Company Name}
        {Date \\ Date}
        [Location]
        \begin{rItemize}
            \item Text.
        \end{rItemize}
    \end{rSubsection}
    \end{rSubsection}
\end{document}

This is the result:

Answer 1

If you want to replace something define low level TeX macros using delimited arguments.

For example

\newcommand{\replaceminus}[1]{\doreplaceminus #1-\relax}

\newcommand{\docreplaceminus}{}% ensure that this helper macro isn't defined yet
\def\doreplaceminus#1-#2\relax{%
  \ifx\relax#2\relax
    #1%
  \else
    #1--\doreplaceminus#2\relax   % replace next - (or remove additional -)
  \fi}

The macro \replaceminus can then used inside your shown rSubsection environment replacement begin text to replace every - in the third argument \replaceminus{#3}.

The helper macro \doreplaceminus assumes an argument with a minus character token (non-active, category code other) and \relax as end of the argument. The macro \replaceminus is defined to provide these two tokens as default. In a first step it is checked if we reached these two tokens, i.e., argument #2 is empty, and we are finished. Otherwise the - is replaced by two minus character tokens and everything starts anew. (The macro uses recursion! To avoid input stack overflows if there are two many minus characters you have to use some well known tricks like \def\EndFi#1\fi{\fi #1} to make the macro expansion end recursive.)

Please be aware of spaces in your input and your macros/environment definitions! My macro \replaceminus doesn't add or remove spaces.

Answer 2

I'm not sure what's preventing you from inputting

date -- date

if you want that. Anyway, you can “normalize” the input.

\documentclass[11pt,letterpaper]{article} % Font size and paper type

\usepackage[parfill]{parskip} % Remove paragraph indentation

\usepackage{enumitem} % For rItemize left margin
\usepackage[left=0.4 in,top=0.4in,right=0.4 in,bottom=0.4in]{geometry} % Document margins

\NewDocumentEnvironment{rSubsection}{mmmo}{%
  \par
  \textbf{#1}, {#2}\IfValueT{#4}{, \textit{#4}}.\hfill\parsedates{#3}%
  \par
}{}

\NewDocumentEnvironment{rItemize}{}
  {\begin{itemize}\raggedright}
  {\end{itemize}}

\ExplSyntaxOn
\NewDocumentCommand{\parsedates}{m}
 {
  \tl_set:Nn \l_tmpa_tl { #1 }
  \regex_replace_once:nnN { \s* (\c{\\}|\-)+ \s* } {\ --\ } \l_tmpa_tl
  \tl_use:N \l_tmpa_tl
 }
\ExplSyntaxOff

\begin{document}
%----------------------------------------------------------------------------------------
% Professional Experience   
%----------------------------------------------------------------------------------------

% double hyphen with spaces
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date -- Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% double hyphen with no spaces
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date--Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% double hyphen with one space
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date-- Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% double hyphen with one space
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date --Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% single hyphen with spaces
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date - Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% single hyphen with no spaces
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date-Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% single hyphen with one space
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date- Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% single hyphen with one space
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date -Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% double backslash with spaces
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date \\ Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% double backslash with no spaces
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date\\Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% double backslash with one space
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date\\ Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

% double backslash with one space
\begin{rSubsection}
  {Role}
  {Company Name}
  {Date \\Date}
  [Location]
  \begin{rItemize}
    \item Text.
  \end{rItemize}
\end{rSubsection}

\end{document}

As you see, the output is always the same.