Best,

Leo

Assuming you have a recent pdfTeX (or XeTeX), then the following implements the same idea as \tl_replace_all_in:Nnn but without expl3:

\documentclass{article}
\makeatletter
\newtoks\replace@toks
\newcommand\replace@all@in[3]{%
  \replace@toks{}%
  \long\def\replace@all@aux##1#2##2\@nil{%
    \if@no@value{##2}%
      {%
        \replace@toks\expandafter\expandafter\expandafter
          {\expandafter\the\expandafter\replace@toks##1}%
      }%
      {%
        \replace@toks\expandafter\expandafter\expandafter
          {\expandafter\the\expandafter\replace@toks##1#3}%
        \replace@all@aux\@empty##2\@nil
      }%
  }%
  \@firstofone{\expandafter\replace@all@aux\expandafter\@empty}%
  #1#2\no@value\@nil
  \edef#1{\the\replace@toks}%
}
\newcommand\replace@all@aux{}
\newcommand\if@no@value[1]{%
  \ifnum\pdfstrcmp{\noexpand\no@value}{\unexpanded{#1}}=\z@\relax
    \expandafter\@firstoftwo
  \else
    \expandafter\@secondoftwo
  \fi
}
\makeatother
\begin{document}
\makeatletter
\def\test{Hello|world}
\replace@all@in\test{|}{ }
\test
\makeatother
\end{document}

This relies on \pdfstrcmp. If it’s not available, then some more code is needed for the comparison test (to do it safely, at least).

Joseph

Thank you for that answer. Unfortunately I don’t plan to use expl3. I will look at it when I become more comfortable with TeX and LaTeX.

Leo

If you are only talking about code you use, then the problem is less pressing: the real troubles start when you write code other people use.

As I explained in my post, if you’re happy to load expl3, then \tl_replace_all_in:Nnn would seem easiest:

\newrobustcmd\multiline[2][c]{%
\setlength{\extrarowheight}{0pt}%
\begin{tabular}{@{}#1@{}}
\def\temp{#2}%
\csname\detokenize{tl_replace_all_in:Nnn}\endcsname
\temp{|}{\tabularnewline}%
\temp
\end{tabular}
}

I’ve stuck with “traditional” category codes here, hence the \csname construction for calling \tl_replace_all_in:Nnn (the \detokenize avoids any issue if _ or : are active). If you want to avoid loading expl3, then it’s a question of implementing search-and-replace yourself. The expl3 version is efficient but quite intricate!

Joseph

I was mainly looking at code-level stuff here. For user input, I tend to think that either XeTeX or LuaTeX are much better choices than trying to make UTF-8 work with pdfTeX. LuaTeX is pretty reasonable for general work now, although the lack of higher level LaTeX support is a bit of a pain (of course, if you use ConTeXt all is well).

Joseph

I got a macro as follows:

\begingroup
\catcode`\|=\active
\gdef|{\tabularnewline}
\endgroup
\newrobustcmd\multiline[2][c]{
\begingroup
\catcode`\|=\active
\setlength{\extrarowheight}{0pt}
\begin{tabular}{@{}#1@{}}
\scantokens{#2}
\end{tabular}
\endgroup
}

How to make this macro safer? thanks.

Leo