[Tex/LaTex] Automatic linebreak in align environment in macros

alignamsmathline-breaking

I have given a selfdefined command like

\newcommand{\AND}[2]{\left(#1 \vee #2 \right)}

which makes sure that I always give the correct number of parameters to my formula and which handles the parentheses as well. Now, when I use this command in a align environment and the arguments become very long, then a linebreak becomes nessecary.

Here's the problem: In the align environment I have to set linebreaks myself, however between \left and \right linebreaks aren't allowed.

So, is there any way to have a automatic linebreak here, which also keeps the correct size of the parentheses?

My only workaround so far is not to use the macro in these situations, which results in unclean code.

The breqn package doesn't seem to fix this problem.

\documentclass[11pt, draft]{scrbook}
\usepackage{amsmath}
\usepackage{breqn}

\newcommand{\AND}[2]{\ensuremath{\left(#1\vee#2\right)}}

\begin{document}
\begin{align*}
aaa&= \AND{\sum^a_b \AND{\AND{\AND{\AND{\AND{\AND{\AND{\AND{\AND{\AND{a}{b}}{b}}{b}}{b}}{\AND{\AND{a}{\AND{a}{b}}}{\AND{a}{\AND{a}{b}}}}}{b}}{b}}{a}}{\AND{a}{\AND{\AND{a}{b}}{b}}}}{\frac{a}{\frac{a}{b}}}}{\sum^a_b \AND{c}{\frac{a}{\frac{a}{b}}}}\\
&= b
\end{align*}
\end{document}

EDIT: After fiddling around for a while, I came up with a small workaround that solves a part of the problem, but not all. I defined a new command which inserts a linebreak and handles the parenthesis for this linebreak:

\documentclass[11pt, draft]{scrbook}
\usepackage{amsmath}
\usepackage{mathtools}

\newcommand{\AND}[2]{\ensuremath{\left(#1\vee#2\right)}}
\newcommand{\ANDbr}[2]{\ensuremath{%
\begin{lgathered}[t]%
\left(#1 \vee \vphantom{#2} \right. \\
\left.\vphantom{#1\vee}#2\right)
\end{lgathered}%
}}

\begin{document}
\begin{align*}
aaa&= \ANDbr{\AND{\AND{\AND{a}{b}}{\AND{\frac{a}{b}}{c}}}{\AND{\AND{\sum_a^b a}{p}}{\AND{a}{b}}}}{\AND{\AND{\AND{a}{b}}{\AND{a}{b}}}{\AND{\AND{a}{b}}{\AND{a}{b}}}}\\
&= b
\end{align*}
\end{document}

This seems to work as long as I need only one linebreak. Inserting \ANDbr for a second time messes things up however.

EDIT2:
I tried to add \allowbreak into the definition of \AND, but it didn't change anything.

Best Answer

I don't recommend using the following code, but it seems to do what you want: I define a command \breaktowidth where you have to specify how wide the block should be inside which line breaks are possible. Then of course \left and \right have to be used in a way such that they don't prevent the line breaks; this is done with a separate command \delimiterswithbreaks.

output

\documentclass[11pt,draft]{scrbook}
\usepackage{mathtools}
\newcommand{\delimiterswithbreaks}[3]{%
  \mathopen{\left#1\vphantom{#3}\right.\hskip-\nulldelimiterspace}
  #3
  \mathclose{\hskip-\nulldelimiterspace\left.\vphantom{#3}\right#2}
  }
\newcommand{\breaktowidth}[2]{\vtop{\hsize#1\noindent$#2$}}
\newcommand{\AND}[2]{\delimiterswithbreaks{(}{)}{#1\vee#2}}
\begin{document}
\begin{align*}
aaa &= \breaktowidth{6cm}{\AND{\AND{\AND{\AND{a}{b}}{\AND{\frac{a}{b}}{c}}}{\AND{\AND{\sum_a^b a}{p}}{\AND{a}{b}}}}{\AND{\AND{\AND{a}{b}}{\AND{a}{b}}}{\AND{\AND{a}{b}}{\AND{a}{b}}}}} \\
    &= b
\end{align*}
\end{document}

Note: mathtools automatically loads amsmath!

Related Solutions

[Tex/LaTex] Automatic linebreak on specific character

I suggest you use the \discretionary command for hyphens.

\documentclass{scrartcl}

\let\underscore\_
\renewcommand{\_}{\discretionary{\underscore}{}{\underscore}}

\begin{document}
\section{Test}
Finally there is a simple solution using  
\textsc{\textbf{XMLResource.OPTION\_RECORD\_UNKNOWN\_FEATURE}} option. And the
text must go on \ldots.
\par
\end{document}

Sample output

Use \discretionary{}{\underscore}{\underscore} instead if you wish the underscore to be placed on the next line, or \discretionary{\underscore}{\underscore}{\underscore} to get the character both before and after the line break.

\discretionary is the hook in to TeX's hyphenation scheme. In some languages, including German, words can change spelling when they are hyphenated, and this command was introduced by Knuth to help cover such situations. \discretionary{a}{b}{c} prints c if there is no linebreak, otherwise it prints a before the linebreak and b after.

If you want to limit this to one particular type of phrase then I suggest you use

\newcommand{\resource}[1]{\textbf{\let\underscore\_
  \renewcommand{\_}{\discretionary{\underscore}{}{\underscore}} #1}}

and write \resource{XMLResource.OPTION\_RECORD\_UNKNOWN\_FEATURE} in your text. (I have removed the \textsc from your example as it had no effect.)

If you wish to use it in one section of the document, then you can similarly define an environment which inserts these definitions at the start, e.g.

\newenvironment{underscoresplit}{\let\underscore\_
  \renewcommand{\_}{\discretionary{\underscore}{}{\underscore}}}{}

used as

\begin{underscoresplit}
  Finally there is a simple solution using 
  \textsc{\textbf{XMLResource.OPTION\_RECORD\_UNKNOWN\_FEATURE}} option. And the
  text must go on \ldots.  
\end{underscoresplit}

[Tex/LaTex] Hbox overfull: automatic linebreaks on spaces

you've already separated the different elements, providing spaces between the distinct equations comprising each language and separately coding these equations as math (even though the space between the first two is, probably inadvertently, omitted). unfortunately, these spaces don't fall in a place that is optimal for tex to break the line.

the ultimate goal is for what is presented to be understood.

there are two parts to this recommendation.

first, the words "milk, curry, rice" are, as you say, constants, and as such should be in a text font, preferably not italic in this context, even though they're part of the math expression. as coded in your original, they are typeset as strings of variables multiplied together. these could be coded as \mathrm{<word>}, but that doesn't help with line breaking. it also wouldn't leave spaces after the commas, although in this situation, whether spaces are visible there or not wouldn't be misunderstood by a reader.

another way to approach these is to recognize them as text, and input them as, for example,

$\mathcal{C}_o=\{\text{milk, curry, rice}\}$

but this doesn't help with line breaking either, since in this context, the only "allowable" break is after the equals sign.

so, second part of suggestion, take advantage of the fact that a reader isn't likely to misunderstand what is meant if a line is broken within that string of constants, and (temporarily) terminate the math after the opening brace, and reinstate it for the ending brace:

$\mathcal{C}_o=\{$milk, curry, rice$\}$

to illustrate, using a forced line break for the "all math" instance, compare these two lines:

enter image description here

here's the input that produced the image:

\begin{itemize}
\item The language of enquiry $\mathcal{L}$ is given by
$\mathcal{C}_o=\{milk, curry, rice\}$,\\
$\mathcal{R}_o=\{TastesHot, IsWhite, ContainsSpice, ContainsSugar\}$,
$\mathcal{F}_o=\{\}$.
\item The language of enquiry $\mathcal{L}$ is given by
$\mathcal{C}_o=\{$milk, curry, rice$\}$,
$\mathcal{R}_o=\{$TastesHot, IsWhite, ContainsSpice, ContainsSugar$\}$,
$\mathcal{F}_o=\{\}$.
\end{itemize}

(by the way, that's hardly a minimal example.)

Best Answer

Related Solutions

[Tex/LaTex] Automatic linebreak on specific character

[Tex/LaTex] Hbox overfull: automatic linebreaks on spaces

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