I'm having trouble with my \newcommand when I have a linebreak inside the argument, it is defined as:
\documentclass{report}
\newcommand{\noblablabla}[2]{\textbf{#1}-#2}
\begin{document}
\noblablabla{aaaabbbb}{xxxx} % this is OK
\noblablabla{aaaa
bbbb}{xxxx}
\end{document}
The first call is OK, the second call gives me the Runaway argument error and the result is the following:
bbbb}{xxxx}
% ^^ up here "Runaway argument"
When I espected some thing like
As suggested in comments, \textbf is designed for short things --- not paragraphs. You can just change to a font-selection command:
\documentclass{report}
\newcommand{\noblablabla}[2]{{\bfseries #1\/}-#2}
\begin{document}
\noblablabla{aaaabbbb}{xxxx} % this is OK
\noblablabla{aaaa
bbbb}{xxxx}
% no more "Runaway argument"
\end{document}
...look carefully at the { placement ;-).
The \/ will perform italic correction if necessary (shouldn't be necessary with a bold typeface, but it is font-dependent); thanks to @Skillmon for pointing it out.
When (La)TeX reads and tokenizes input under standard catcode-régime with standard-value for the integer-parameter \endlinechar, two consecutive endline-characters—in the .tex-input file they yield an empty line—get tokenized as the token \par which usually serves for ending the current paragraph (and having (La)TeX start a new paragraph in case material which triggers switching to horizontal mode follows).
In (La)TeX macros come in two flavours:
\par is allowed in the arguments. These are so-called "long macros" because when you wish to define such a macro by means of TeX primitives like \def or \edef or \gdef or \xdef, you need to add the prefix \long to the definition-primitive in use. \par is not allowed in the arguments. Many people call them "short macros" because when defining them you omit the \long-prefix. When an argument of a short macro contains the token \par, then you get an error-message about "Runaway argument?... Paragraph ended before ... was complete".\textbf is defined to call such a such a "short" macro whose name is \text@command, and to pass its argument as argument to that macro. Therefore the error message. You can easily circumvent that message by not having the token \par within the argument and instead having, e.g., the token sequence \csname par\endcsname in the argument, or the token \myparcopy after \let\myparcopy=\par:
\documentclass{report}
\newcommand{\noblablabla}[2]{\textbf{#1}-#2}
\begin{document}
\noblablabla{aaaabbbb}{xxxx} % this is OK
\noblablabla{aaaa\csname par\endcsname bbbb}{xxxx}
\end{document}
\documentclass{report}
\newcommand\myparcopy{}%
\newcommand{\noblablabla}[2]{\textbf{#1}-#2}
\begin{document}
\noblablabla{aaaabbbb}{xxxx} % this is OK
\let\myparcopy=\par
\noblablabla{aaaa\myparcopy bbbb}{xxxx}
\end{document}
\myparcopy under the name \endgraf
– Phelype Oleinik
Sep 18 '19 at 23:44
\endgraf is: \endgraf is intended to be a copy of the primitive \par while the \long-mechanism aims at the control word token token \par regardless its meaning. So \endgraf as \parcopy is possible only as long as \par still has the meaning of the primitive. You can redefine \par, e.g., to expand to "I should have my socks stuffed, but my UNIVAC has no app for that" and with a macro not defined in terms of \long you still get runaway argument errors in case of one of its arguments containing the token \par.
– Ulrich Diez
Sep 19 '19 at 18:25
\par like that then they probably know what they're doing ;-) But yes, your reasoning is more cautious.
– Phelype Oleinik
Sep 19 '19 at 18:55
\myparcopy-assignment right before \noblablabla, not into the preamble. I don't know what I was thinking there. In any case I would redefine \par only in ways where the last thing carried out is \endgraf. ;-)
– Ulrich Diez
Sep 19 '19 at 20:46
\textbfforwards its argument to\text@command, which is declared as a short macro, so it can't contain a\parin its argument. You can circumvent this by using\endgrafinstead of the two consecutive newlines, but I don't think it is a good idea and you should change your macro if you want to have a newline there. – Skillmon Sep 18 '19 at 07:36\textbf{#1}to{\bfseries #1}. Why?\bfseriescan handle paragraph breaks -- recall that an all-blank input line generates a paragraph break -- in its scope, whereas\textbfcan not. – Mico Sep 18 '19 at 07:53{<fontswitch> #1}to<textcommand>{#1}, the former doesn't apply any italic correction whereas the latter would (though this shouldn't be an issue for\textbf, it could for\textit). – Skillmon Sep 18 '19 at 08:10{\itshape #1\/}? Not sure, so I am not modifying the answer... is italic correction dependent on the current font, the next font or both? – Rmano Sep 18 '19 at 09:03\/should be correct (it's dependent on the current font and the last symbol in#1and might be dependent on the next symbol in the following text). – Skillmon Sep 18 '19 at 09:18