I am writing a lemma in math which is the following using the italics parameter \textit but need to insert plain text that isn't italicized in the lemma. I can't just delete the \textit around my math lemma or else the lemma won't be in italics.
[Tex/LaTex] Plain text in italics
italic
Related Solutions
For the underscore, the following works:
\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lmodern}
\usepackage[ngerman]{babel}
\catcode`\_=\active
\protected\def_{\begingroup\itshape\aftergroup\/\let_\endgroup}
\begin{document}
Hello \textit{World!} How are you?
Hello _World!_ How are _you?
I'm fine._ And you?
_I'm fine, too.
Glad to hear that._
\end{document}
However, it is a bit crazy and unstable. If you want to use it only for short texts (not spanning multiple paragraphs), the following would be better. (It doesn't work in the above example, since there we span multiple pagraphs. In real, it will throw an error if you put odd number of _ in one paragraph.)
\catcode`\_=\active
\protected\def_#1_{\textit{#1}}
You can use the same ideas for the star. The problem is, that \section*{Text} will suddenly stop working. Variant 1:
\catcode`\*=\active
\protected\def*{\begingroup\bfseries\let*\endgroup}
Variant 2:
\catcode`\*=\active
\protected\def*#1*{\textbf{#1}}
If you don't use math at all, just use ^ instead of * and it should be ok.
How does it work: The primitive macro \catcode makes _ \active so that we can define it as any other command.
In Variant 1, we define it to (1) start a group (2) start italic text (3) add italic correction to the end of the italic text (4) make the one next _ end the group we started. By the end of the group, the re-definition of _ is forgotten so another _ will again start an italic text.
The Variant 2 is even simpler: When _ is found, a second _ is looked for, end everything inbetween is put into \textit.
The \protected directive makes sure that _ is written as _ in the auxiliary files, which is necessary for it to behave correctly.
Here are some options, depending on whether you want the text to stand out or not:
\documentclass{article}
\usepackage{lipsum}
\newenvironment{itquote}
{\begin{quote}\itshape}
{\end{quote}\ignorespacesafterend}
\newenvironment{itpars}
{\par\itshape}
{\par}
\begin{document}
\lipsum[1]
\begin{quote}
\lipsum[2]
\end{quote}
\lipsum[3]
\begin{itquote}
\lipsum[2]
\end{itquote}
\lipsum[4]
\begin{itpars}
\lipsum[2]
\end{itpars}
\lipsum[5]
\end{document}
The main principle is to use the declaration \itshape rather than a macro (like \textit).
Best Answer
You could just stop the command, then restart it.
Would produce