How to typeset an em dash in an alltt environment

Question

I am trying to typeset an em dash using --- inside an alltt environment, but I get three hyphens instead of a single em dash.

MWE

\documentclass[12pt]{article}

\usepackage{alltt}

\begin{document}
Usually, \verb"---" becomes an em dash, i.e. "---", in normal mode.
But in the alltt environment, it becomes three hyphens.
\begin{alltt}
Please---will you give me an em dash?
\end{alltt}
\end{document}

Response to comments The comments asked why I want to typeset an em dash in a monospaced environment. I would like to typeset a dash that looks like an em dash, but takes the length of two spaces in a monospaced environment, i.e. like "--" but joined together to form a single em dash like character.

An em-dash doesn't make much sense in a monospaced font, does it? — egreg, Sep 22 '14 at 17:45
@egreg Indeed, I now have changed my question to ask for something different that fits in a monospaced environment. — I Like to Code, Sep 22 '14 at 18:19

score 4 · Accepted Answer · edited Apr 13 '17 at 12:35

My suggestion would be to "conceal" it in the form of a macro where the em-dash it taken from \normalfont:

enter image description here

\documentclass{article}
\newcommand{\emdash}{{\normalfont ---}}
\usepackage{alltt}

\begin{document}
Usually, \verb"---" becomes an em dash, i.e. ``---'', in normal mode.
But in the alltt environment, it becomes three hyphens.
\begin{alltt}
Please\emdash{}will you give me an em dash?
\end{alltt}
\end{document}

Unless the mono-spaced font comes with an em-dash, it will be set as separate dashes. You could force a mono-spaced-looking em-dash, perhaps with a definition for \emdash that resembles:

enter image description here

\documentclass{article}
\makeatletter
\newlength{\emdashttlen}
\settowidth{\emdashttlen}{\ttfamily---}
\newcommand{\emdash}{\makebox[\emdashttlen]{-\cleaders\hbox{\hspace{-.45ex}-}\hfill\kern0pt}}
\makeatother
\usepackage{alltt}

\begin{document}
Usually, \verb"---" becomes an em dash, i.e. ``---'', in normal mode.
But in the alltt environment, it becomes three hyphens.
\begin{alltt}
Please---will you give me an em dash?
Please\emdash{}will you give me an em dash?
\end{alltt}

\end{document}

Some information on leaders can be found in Want to fill line with repeating string.

wouldn't you want a dash that's a multiple of the character width, to preserve monospacing? — David Carlisle, Sep 22 '14 at 17:57
Setting \emdashttlen in the preamble will not give a correct length when \small, \footnotesize or another size changing command is in force. — egreg, Sep 22 '14 at 19:52

score 2 · Answer 2 · edited Jun 10 '20 at 12:32

Simple solution: use UTF-8

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{alltt,etoolbox}
\apptocmd{\alltt}{\def\textemdash{{\fontfamily{cmvtt}\selectfont---}}}{}{}
\begin{document}
\begin{alltt}
Please—will you give me an em dash?
Please--will you give me an em dash?
\end{alltt}
\end{document}

Note that the first line contains — (Unicode U+2014 EM DASH)

enter image description here

Overcomplicated solution: fake an em-dash, because the font family hasn't a variable width typewriter font

\documentclass{article}
\usepackage{alltt,etoolbox}
\usepackage{tgcursor}
\makeatletter
\begingroup\lccode~=-
\lowercase{\endgroup\apptocmd{\alltt}{\let~\alltthyphen}{}{}
\newcommand\alltthyphen{@ifnextchar~{@alltthyphen@i}{\char\- }} \def\@alltthyphen@i#1{% #1 is - \@ifnextchar~{\fake@em@dash\@gobble}{\char-\char`- }%
}}
\def\fake@em@dash{%
  \sbox0{--}%
  \makebox[\wd0][s]{-\hss-\hss-}%
}
\makeatother
\begin{document}
\begin{alltt}
Please---will you give me an em dash?
PleaseXXwill you give me an em dash?
\end{alltt}
\end{document}

enter image description here

You might want to simplify the setting using just -- instead of ---; this would need changes to the macros above.

How to typeset an em dash in an alltt environment

2 Answers2

Simple solution: use UTF-8

More complicated solution: transform `---` into `{\fontfamily{cmvtt}\selectfont---}`

Overcomplicated solution: fake an em-dash, because the font family hasn't a variable width typewriter font

How to typeset an em dash in an alltt environment

2 Answers2

Simple solution: use UTF-8

More complicated solution: transform --- into {\fontfamily{cmvtt}\selectfont---}

Overcomplicated solution: fake an em-dash, because the font family hasn't a variable width typewriter font

More complicated solution: transform `---` into `{\fontfamily{cmvtt}\selectfont---}`