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\lyxformat 221
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\options draft
\language english
\inputencoding auto
\fontscheme default
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\float_placement b
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\papersize Default
\paperpackage a4
\use_geometry 0
\use_amsmath 1
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\quotes_times 2
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\layout Title

How to deal with underfull and overfull boxes
\layout Author

Gady Kozma
\layout Date

July 17th, 2004
\layout Section

What are we talking about?
\layout Standard

Like all wordprocessing software, LaTeX, and therefore LyX, will encounter
 from time to time a situation where it is unable to divide text into lines
 or divide the paper into pages in an aesthetic manner.
 Unlike some other wordprocessors, LaTeX will complain about it, by printing
 messages like 
\family typewriter 
overfull hbox
\family default 
 and 
\family typewriter 
underfull vbox
\family default 
.
 More notably
\begin_inset Foot
collapsed false

\layout Standard

A third difference between LaTeX and some other word processors which is
 perhaps less notable, but important nonetheless, is the fact that LaTeX
 breaks lines in a more-than-average intelligent manner.
 Specifically, if LaTeX encounters a problem in a certain line, it can rearrange
 all lines leading up to it.
 As a result, it is less likely that LaTeX will have problems breaking any
 line after the second line of a given paragraph.
\end_inset 

, its reaction to the first problem is not to create a line with enormous
 white gaps but to create a line that sticks out of the margin.
\layout Standard

Unfortunately, LyX doesn't have a very convenient mechanism to find the
 places in the document where LaTeX thought there were problems of this
 kind.
 Thus you must use either of the following methods: choose 
\family sans 
\bar under 
V
\bar default 
iew\SpecialChar \menuseparator

\bar under 
L
\bar default 
atex\SpecialChar ~
Logfile
\family default 
 and search for the error messages, or, usually easier, choose 
\family sans 
\bar under 
F
\bar default 
ile\SpecialChar \menuseparator

\bar under 
E
\bar default 
xport\SpecialChar \menuseparator

\bar under 
L
\bar default 
atex
\family default 
 and use a terminal to run LaTeX directly, i.e.\SpecialChar ~
type the command 
\family typewriter 
latex myfile.tex
\family default 
.
 LaTeX will spew out mysterious error messages, among them the infamous
 
\family typewriter 
overfull hbox
\family default 
 and 
\family typewriter 
underfull vbox
\family default 
 messages.
\layout Standard

Always remember that these problems are 
\emph on 
very
\emph default 
 sensitive to font, font size, and page size.
 Therefore if this is not the final version of the document, if at all possible,
 just ignore them.
 The time to handle them is when your work has taken on its final form.
 And don't worry about this too much.
 It shouldn't take you more than a few minutes work per 10 pages to fix
 even a complicated document.
\layout Standard

Before using all the sophisticated techniques discussed here always remember
 it might be easier to just change the formulation of the text a little.
 Hey, don't give me that look! Cosi Fanni Tutti.
\layout Section

Overfull hboxes
\layout Standard

An 
\begin_inset Quotes eld
\end_inset 

hbox
\begin_inset Quotes erd
\end_inset 

 is an object that LaTeX tries to fill horizontally, typically a line.
 It's 
\begin_inset Quotes eld
\end_inset 

overfull
\begin_inset Quotes erd
\end_inset 

 when LaTeX cannot push all the things it wants to into the line.
 The reason is typically a long word or a formula at the end which, if pushed
 to the next line would make the line too spacey.
 So LaTeX calls for help.
 Here is where you step in.
\layout Standard

Before you start, check if the complaint is for real.
 LaTeX will sometimes complain about hardly noticeable problems.
 If you cannot spot the problem immediately, one solution is as follows:
 in the 
\family sans 
E
\bar under 
x
\bar default 
tra\SpecialChar ~
options
\family default 
 box of the 
\family sans 
\bar under 
D
\bar default 
ocument
\family default 
 tab of 
\family sans 
\bar under 
L
\bar default 
ayout\SpecialChar \menuseparator

\bar under 
D
\bar default 
ocument
\family default 
 add the word 
\family typewriter 
draft
\family default 
.
\begin_inset Foot
collapsed false

\layout Standard

Note that this will have other effects.
 For example, all pictures will be replaced by empty rectangles in the output.
\end_inset 

 In most document classes (in particular the standard and AMS classes) this
 will cause a small black box to be printed to the right of the problematic
 line.
 If you cannot see the problem --- good for you.
 Ignore it and move on to the next error.
 Otherwise proceed reading.
\layout Standard


\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
begin{sloppypar}
\end_inset 

The second easiest solution (after ignoring the problem) is being sloppy
 about it.
\begin_inset Foot
collapsed false

\layout Standard

The paragraph with the footnote mark, for example, if set like that.
 Notice the extra wide space in this line! This is due to sloppily pushing
 the text 
\family typewriter 

\backslash 
end{sloppypar}
\family default 
 to the next line.
\end_inset 

 This is done by the LaTeX commands 
\family typewriter 

\backslash 
begin{sloppypar}
\family default 
 and 
\family typewriter 

\backslash 
end{sloppypar}
\family default 
.
 To enter them, change to TeX mode (a.k.a Evil Red Text) --- use 
\family sans 
\bar under 
I
\bar default 
nsert\SpecialChar \menuseparator

\bar under 
T
\bar default 
eX
\family default 
 --- and write 
\family typewriter 

\backslash 
begin{sloppypar}
\family default 
 in the beginning of the paragraph and 
\family typewriter 

\backslash 
end{sloppypar}
\family default 
 at the end.
 Your lines will contain too much space, but at least they won't stick out
 of the margins.
 If you don't want to do that on a paragraph by paragraph basis, just put
 
\family typewriter 

\backslash 
sloppy
\family default 
 in your preamble (use 
\family sans 
\bar under 
L
\bar default 
ayout\SpecialChar \menuseparator
P
\bar under 
r
\bar default 
eamble
\family default 
, or, in LyX Qt, use 
\family sans 
\bar under 
L
\bar default 
ayout\SpecialChar \menuseparator

\bar under 
D
\bar default 
ocument
\family default 
 and move to the 
\family sans 
Preamble
\family default 
 section) or where you want the sloppy mode to start (use TeX mode).
 The opposite of 
\family typewriter 

\backslash 
sloppy
\family default 
 is 
\family typewriter 

\backslash 
fussy
\family default 
, the default behavior.
 Both commands take effect from the beginning of the paragraph (or part
 thereof, if you have a display formula) where they are found.
\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
end{sloppypar}
\end_inset 


\layout Standard

If the problem is a long word which LaTeX cannot, or would not, hyphenate,
 the simplest solution is to add a hyphenation mark where you think the
 word should be broken.
 Use 
\family sans 
\bar under 
I
\bar default 
nsert\SpecialChar \menuseparator

\bar under 
S
\bar default 
pecial Character\SpecialChar \menuseparator
Hyphenation\SpecialChar ~

\bar under 
P
\bar default 
oint
\family default 
.
 If you want the word to be broken but do not want a hyphen to appear (for
 example, you are breaking a URL
\begin_inset Foot
collapsed false

\layout Standard

If you enter a URL, the easiest method is 
\family sans 
\bar under 
I
\bar default 
nsert\SpecialChar \menuseparator

\bar under 
U
\bar default 
RL
\family default 
 which in most LaTeX installations also takes care of breaking lines for
 you.
 Note though that the LaTeX system in 
\family typewriter 
arXiv.org
\family default 
 is an exception and won't break URLs across lines, so if you plan to submit
 your paper there, plan ahead.
\end_inset 

) you need to add the TeX command 
\family typewriter 

\backslash 
linebreak
\family default 
.
 Notice that this is 
\series bold 
not 
\series default 
the same as 
\family sans 
\bar under 
I
\bar default 
nsert\SpecialChar \menuseparator

\bar under 
S
\bar default 
pecial Character\SpecialChar \menuseparator

\bar under 
L
\bar default 
inebreak
\family default 
! This will force LaTeX to break in that point.
 Usually, however, you would want to use 
\family typewriter 

\backslash 
linebreak[
\family default 

\begin_inset Formula $n$
\end_inset 


\family typewriter 
]
\family default 
, which only recommends to LaTeX to break the line there rather than forces
 it to do so.
 The number 
\begin_inset Formula $n$
\end_inset 

 is the level of recommendation, from 0 to 4, with 
\family typewriter 

\backslash 
linebreak[0]
\family default 
 being the weakest (and usually what you want) and 
\family typewriter 

\backslash 
linebreak[4]
\family default 
 the strongest, and equivalent to just 
\family typewriter 

\backslash 
linebreak
\family default 
.
 Using this method instead of simply 
\family typewriter 

\backslash 
linebreak
\family default 
 will mean that you'll have less work the 
\emph on 
next
\emph default 
 time you change font.
 
\layout Standard

More about this can be found in 
\family typewriter 
http://dont.really.go.there/this/
\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
linebreak[0]
\end_inset 

is/
\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
linebreak[0]
\end_inset 

just/
\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
linebreak[0]
\end_inset 

to/demonstrate/how/this/works
\family default 
.
\layout Subsection

Inline formulas
\layout Standard

Formulas inside you text pose more of a problem as LaTeX is typically shy
 of breaking formulas, and many authors consider breaking formulas across
 lines an ugly habit
\begin_inset Foot
collapsed false

\layout Standard

Section 
\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
ref{ssec:agrevate}
\end_inset 

 is for you guys.
 Naturally, using the techniques there will only aggravate overfull hbox
 problems.
\end_inset 

.
 The first option you should consider is probably to make the formula into
 a display formula (
\family sans 
\bar under 
I
\bar default 
nsert\SpecialChar \menuseparator
Mat
\bar under 
h
\bar default 
\SpecialChar \menuseparator

\bar under 
D
\bar default 
isplay\SpecialChar ~
Formula
\family default 
).
 If you want to keep the formula inline, you can try the 
\family typewriter 

\backslash 
linebreak
\family default 
 mechanism above.
 Notice that to create evil red text in math mode you don't need to select
 it from a menu, it is activated automatically by the 
\family typewriter 

\backslash 

\family default 
 sign and terminated by the 
\family typewriter 
[
\family default 
 --- the 
\family typewriter 
[0]
\family default 
 will not appear in red but don't worry about it.
 In many cases it works inside formulas.
 The main case where it doesn't is inside grouped parenthesis, by which
 I mean parenthesis entered using the parenthesis button in the math panel
 (
\family sans 
\bar under 
I
\bar default 
nsert
\family default 
\SpecialChar \menuseparator

\family sans 
Mat
\bar under 
h
\family default 
\bar default 
\SpecialChar \menuseparator

\family sans 
Math\SpecialChar ~
Pane
\bar under 
l
\family default 
\bar default 
).
 LaTeX will simply ignore 
\family typewriter 

\backslash 
linebreak
\family default 
 commands inside a grouped parenthesis.
 Here is an example:
\layout Quote

I love long formulas in the middle of my text, like 
\begin_inset Formula $\int1/(t\log t\log\log t\linebreak\log\log\log t)\, dt=\log\log\log\log x$
\end_inset 

.
 But when I write 
\begin_inset Formula $\log\left(\sin x+\cos x+\linebreak\tan x\right)$
\end_inset 

 the grouped parenthesis always makes my formulas stick to the right.
\layout Standard

The solution is to replace them with regular parenthesis.
 You would probably want to enlarge them, though.
 To do that, just write 
\family typewriter 

\backslash 
big
\family default 
 before each parenthesis.
 If 
\family typewriter 

\backslash 
big
\family default 
 is not big enough, just try 
\family typewriter 

\backslash 
Big
\family sans 
, 
\family typewriter 

\backslash 
bigg
\family sans 
 
\family default 
or 
\family typewriter 

\backslash 
Bigg
\family default 
.
 Table 
\begin_inset LatexCommand \ref{tbl:bigBigg}

\end_inset 

 shows how they look.
\begin_inset Float table
placement htbp
wide false
collapsed false

\layout Standard
\align center 

\begin_inset  Tabular
<lyxtabular version="3" rows="5" columns="2">
<features>
<column alignment="center" valignment="top" leftline="true" rightline="true" width="0pt">
<column alignment="center" valignment="top" leftline="true" rightline="true" width="0pt">
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard

regular
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\begin_inset Formula $([\{|\}])\langle\lfloor\lceil/\uparrow\Uparrow\Downarrow\downarrow\backslash\rceil\rfloor\rangle$
\end_inset 


\end_inset 
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\family typewriter 

\backslash 
big
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\begin_inset Formula $\big(\big[\big\{\big|\,\big\}\big]\big)\big\langle\big\lfloor\big\lceil\big/\big\uparrow\big\Uparrow\big\Downarrow\big\downarrow\big\backslash\big\rceil\big\rfloor\big\rangle$
\end_inset 

 
\end_inset 
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\family typewriter 

\backslash 
Big
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\begin_inset Formula $\Big(\Big[\Big\{\Big|\Big\}\Big]\Big)\Big\langle\Big\lfloor\Big\lceil\Big/\Big\uparrow\Big\Uparrow\Big\Downarrow\Big\downarrow\Big\backslash\Big\rceil\Big\rfloor\Big\rangle$
\end_inset 


\end_inset 
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\family typewriter 

\backslash 
bigg
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\begin_inset Formula $\bigg(\bigg[\bigg\{\bigg|\bigg\}\bigg]\bigg)\bigg\langle\bigg\lfloor\bigg\lceil\bigg/\bigg\uparrow\bigg\Uparrow\bigg\Downarrow\bigg\downarrow\bigg\backslash\bigg\rceil\bigg\rfloor\bigg\rangle$
\end_inset 

 
\end_inset 
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard
\align center 

\family typewriter 

\backslash 
Bigg
\end_inset 
</cell>
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\layout Standard


\begin_inset Formula $\Bigg(\Bigg[\Bigg\{\Bigg|\Bigg\}\Bigg]\Bigg)\Bigg\langle\Bigg\lfloor\Bigg\lceil\Bigg/\Bigg\uparrow\Bigg\Uparrow\Bigg\Downarrow\Bigg\downarrow\Bigg\backslash\Bigg\rceil\Bigg\rfloor\Bigg\rangle$
\end_inset 


\end_inset 
</cell>
</row>
</lyxtabular>

\end_inset 


\layout Caption


\begin_inset LatexCommand \label{tbl:bigBigg}

\end_inset 

parenthesis and friends in various sizes.
\end_inset 


\layout Standard

Apropos table 
\begin_inset LatexCommand \ref{tbl:bigBigg}

\end_inset 

, one should be careful to distinguish between the symbols 
\begin_inset Formula $\langle$
\end_inset 

 and 
\begin_inset Formula $\rangle$
\end_inset 

 use for scalar product and bra-ket notation and the simple bigger/smaller
 signs 
\begin_inset Formula $<>$
\end_inset 

.
 Not only are they different in appearance, TeX will also space them differently.
 There is no GUI for entering the symbols 
\begin_inset Formula $\langle$
\end_inset 

, 
\begin_inset Formula $\rangle$
\end_inset 

, nor for the symbols 
\begin_inset Formula $\lfloor$
\end_inset 

, 
\begin_inset Formula $\lceil$
\end_inset 

,
\begin_inset Formula $\backslash$
\end_inset 

, 
\begin_inset Formula $\rceil$
\end_inset 

, 
\begin_inset Formula $\rfloor$
\end_inset 

 --- from the math panel you can only insert the grouped version, not the
 
\begin_inset Quotes eld
\end_inset 

stand alone
\begin_inset Quotes erd
\end_inset 

 version.
 I simply enter them using their TeX shortcuts and LyX understands and transform
s them to the appropriate characters automatically.
 The shortcuts are, respectively, 
\family typewriter 

\backslash 
langle
\family default 
, 
\family typewriter 

\backslash 
rangle
\family default 
, 
\family typewriter 

\backslash 
lfloor
\family sans 
, 
\family typewriter 

\backslash 
lceil
\family sans 
, 
\family typewriter 

\backslash 
backslash
\family default 
 or 
\family typewriter 

\backslash 

\backslash 

\family default 
, 
\family typewriter 

\backslash 
rceil
\family sans 
, 
\family typewriter 

\backslash 
rfloor
\family default 
.
 
\layout Standard

If you use inverted parenthesis, as for example in the old-fashioned style
 
\begin_inset Formula $\left]0,1\right[$
\end_inset 

, you need to tell LaTeX which is left and which is right in order for it
 to get the spacing right.
 You do that by replacing the various 
\family typewriter 

\backslash 
big
\family default 
 constructs with 
\family typewriter 

\backslash 
bigl
\family default 
 and 
\family typewriter 

\backslash 
bigr
\family default 
.
 For example
\begin_inset Note
collapsed false

\layout Standard

will do the spacing correctly 
\series bold 
only
\series default 
 if you insert them as grouped parenthesis.
 If you have line-breaking problems with these constructs, and you converted
 them into non-grouped parenthesis, you will have to tweak the spacing yourself.
 This is explained in the 
\emph on 
User's Guide
\emph default 
, as of this writing in section 5.1.8, 
\emph on 
Altering Spacing
\emph default 
.
\end_inset 


\layout Quote


\begin_inset Formula $I=\bigl]0,1\bigr[$
\end_inset 

 looks much better than 
\begin_inset Formula $I=\bigr]0,1\bigl[$
\end_inset 

.
 Notice how the 
\begin_inset Formula $=$
\end_inset 

 and the 
\begin_inset Formula $]$
\end_inset 

 are cramped together in the second example, which has the right and left
 
\family typewriter 

\backslash 
big
\family default 
 commands reversed.
 
\layout Standard

There is also a 
\family typewriter 

\backslash 
bigm
\family default 
 construct for notations such as 
\begin_inset Formula $\mathbb{P}\bigl(X\bigm|Y\bigr)$
\end_inset 

.
\layout Standard

There are corresponding constructs specific for 
\begin_inset Formula $|$
\end_inset 

 signs --- the commands 
\family typewriter 

\backslash 
lvert
\family default 
 and 
\family typewriter 

\backslash 
rvert
\family default 
.
 I cannot in honesty vouch for or against them.
 Check the documentation for the 
\family sans 
amsmath
\family default 
 package which should come with your TeX distribution --- try e.g.
 
\family typewriter 
/usr/share/texmf/doc/latex/amsmath/amsldoc.dvi
\family default 
 --- where these things are thoroughly explained.
\layout Subsection

Display formulas
\layout Standard

Display formulas can also be too long, quite easily so in fact, and will
 create an 
\family typewriter 
overfull hbox
\family default 
 warning.
 There isn't much to do about it except transform them into multi-line equations.
 Multi-line equations are covered quite fully in the 
\emph on 
User's Guide
\emph default 
 (as of writing this, in section 5.4).
\layout Standard

As in the case of inline equations, you might need to break parenthesis
 across lines and run into various problems.
 The simplest solution is to use the 
\begin_inset Quotes eld
\end_inset 

no parenthesis
\begin_inset Quotes erd
\end_inset 

 square at the bottom right corner of the parenthesis panel (remember to
 uncheck the 
\family typewriter 
\bar under 
K
\bar default 
eep matched
\family default 
 box if you are using LyX Qt), for example
\begin_inset Formula \begin{eqnarray*}
f(n) & = & \pi\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\dotsb\right.\\
 &  & \left.\dotsb+\frac{n-2}{n-1}+\frac{n-1}{n}\right)\end{eqnarray*}

\end_inset 

But what if there were no fractions on the bottom line? The parenthesis
 would come out too small.
 Obviously, one could solve this using the 
\family typewriter 

\backslash 
big
\family default 
, 
\family typewriter 

\backslash 
Big
\family default 
, 
\family typewriter 

\backslash 
bigg
\family default 
 etc.\SpecialChar ~
mechanism.
 But there is another solution, using the 
\family typewriter 

\backslash 
vphantom
\family default 
 LaTeX command.
 Let us demonstrate with an example
\begin_inset Formula \begin{align*}
 & \left(\sum_{i=1}^{\infty}\textrm{The parenthesis on this line are large due to the }\sum\textrm{ sign,}\right.\\
 & \left.\textrm{so lets add here a vphantom command with the same construct}\vphantom{\sum_{i=1}^{\infty}}\right).\end{align*}

\end_inset 

For those reading the printed version, the lower line has a 
\family typewriter 

\backslash 
vphantom{
\family default 

\begin_inset Formula ${\displaystyle \sum_{i=1}^{\infty}}$
\end_inset 


\family typewriter 
}
\family default 
 which doesn't appear at all, but makes the parenthesis large.
 You can put anything you want inside the 
\family typewriter 
{}
\family default 
 signs --- whatever you put does not show but its height is considered when
 the line height is calculated.
\layout Standard

There is nothing stopping you from using the 
\family typewriter 

\backslash 
vphantom
\family default 
 trick on inline formulas, but it really more suitable for using in large,
 complicated display formulas.
\layout Subsection

More on hyphenation
\layout Standard

There are a number of issues you might want to know about if you have hyphenatio
n problems.
 First of all, hyphenation is language sensitive.
 Really! You can change the default language of the document via the 
\family sans 
Language
\family default 
 tab of the
\family sans 
 
\bar under 
L
\bar default 
ayout\SpecialChar \menuseparator

\bar under 
D
\bar default 
ocument
\family default 
 popup, or you can change a particular piece of text via the 
\family sans 
\bar under 
L
\bar default 
ayout\SpecialChar \menuseparator

\bar under 
C
\bar default 
haracter
\family default 
 popup.
 A typical LaTeX installation will support hyphenation in English, French,
 German, Spanish, Russian and a few others.
\layout Standard

The second thing you have to know is that there is a package to help with
 hyphenation problems: 
\family typewriter 
hyphenat
\family default 
.
 The most popular uses of 
\family typewriter 
hyphenat
\family default 
 are to turn hyphenation off completely, or to allow hyphenation of text
 in the 
\family typewriter 
typewriter
\family default 
 font,
\begin_inset Foot
collapsed false

\layout Standard

By default, any text in typewriter font is never hyphenated.
 URLs are only a specific case.
\end_inset 

 and it has some advanced tools in addition.
 More likely than not, it is a part of your LaTeX distribution.
 Read the documentation, it could be in, for example, 
\family typewriter 
/usr/share/texmf/doc/latex/styles/hyphenat.dvi
\family default 
.
\layout Standard

Finally, there are special cases where you want special effects when the
 line is broken --- not just any old hyphen.
 For these unusual cases, you need the 
\family typewriter 

\backslash 
discretionary
\family default 
 command.
 Since this is a bit off topic, I've put the full description in an appendix.
 
\layout Subsection


\begin_inset LatexCommand \label{ssec:agrevate}

\end_inset 

More on breaking inline formulas
\layout Standard

LaTeX (and TeX) will break inline formulas around equality-like signs, e.g.\SpecialChar ~

\begin_inset Formula $=$
\end_inset 

, 
\begin_inset Formula $\approx$
\end_inset 

, 
\begin_inset Formula $\leq$
\end_inset 

 etc., and less willingly around binary operators like 
\begin_inset Formula $+$
\end_inset 

, 
\begin_inset Formula $\cdot$
\end_inset 

, 
\begin_inset Formula $\wedge$
\end_inset 

.
 To make LaTeX less or more likely to break formulas in that way, do the
 following: in the latex preamble add the following commands:
\layout LyX-Code


\backslash 
relpenalty=
\begin_inset Formula $n$
\end_inset 


\layout LyX-Code


\backslash 
binoppenalty=
\begin_inset Formula $m$
\end_inset 


\layout Standard

where 
\begin_inset Formula $n$
\end_inset 

 and 
\begin_inset Formula $m$
\end_inset 

 are two numbers that tell LaTeX how bad is it to break formulas around
 equality-like signs and binary operators respectively.
 The default values (for both TeX and LaTeX) are 500 and 700.
 The value 10000 is used as 
\begin_inset Formula $\infty$
\end_inset 

 so if you set either to 10000 TeX will never break your formulas in that
 kind of position.
\layout Subsection

Underfull hboxes
\layout Standard

These are quite rare, but can happen, e.g.\SpecialChar ~
when you use forced linebreaks.
 Here is an example:
\layout Quote

Wow, why is this line like that?
\begin_inset ERT
status Collapsed

\layout Standard

\backslash 
linebreak 
\end_inset 

Oh, because I asked so explicitly.
 Silly me.
\layout Standard

Similarly, the use of 
\family typewriter 
sloppypar
\family default 
 can cause 
\family typewriter 
underfull hbox
\family default 
 errors.
\layout Section

Underfull vboxes
\layout Standard

A vbox is something that LaTeX tries to fill vertically, typically a page.
 For some unknown reason, when LaTeX cannot fill the page because the last
 object is too large, it will not do as it does for lines and go over the
 margins, but it will prefer to put the offending object on the next page.
 Hence the error will usually be 
\family typewriter 
underfull vbox
\family default 
 and the visible symptom will be pages which are too short, have too much
 space between the text and the footnotes or that have too much space between
 paragraphs, formulas etc.
\layout Standard

The range of solutions to underfull vboxes is more restricted.
 Most notably it is to tell LaTeX where to break pages yourself.
 This is covered in the 
\emph on 
User's Guide
\emph default 
 under 
\begin_inset Quotes eld
\end_inset 

forcing page breaks
\begin_inset Quotes erd
\end_inset 

 (as of the time of writing, this is subsection 6.4.4).
 Unfortunately, in many cases the offending object is a multi-line formula,
 and you cannot enter a pagebreak inside a formula using the 
\family sans 
\bar under 
L
\bar default 
ayout\SpecialChar \menuseparator

\bar under 
P
\bar default 
aragraph
\family default 
 popup.
 A simple solution might be to break the formula into two formulas, possibly
 forcing a pagebreak between them, but actually there's a better way so
 read on.
\layout Standard

It is possible to allow page breaks inside formulas, globally or on a formula-by
-formula basis.
 To understand how, we first need to differentiate between LaTeX formula
 environment and AMS formula environments.
 The (regular) LaTeX formula environment are what you get when you hit 
\family sans 
C-Return
\family default 
 inside a formula, or by choosing 
\family sans 
\bar under 
I
\bar default 
nsert\SpecialChar \menuseparator
Mat
\bar under 
h
\bar default 
\SpecialChar \menuseparator

\bar under 
E
\bar default 
qnarry\SpecialChar ~
environment
\family default 
.
 The AMS formula environment are supported in LyX using 
\family sans 
\bar under 
I
\bar default 
nsert\SpecialChar \menuseparator
Mat
\bar under 
h
\bar default 
\SpecialChar \menuseparator
AMS\SpecialChar ~
*
\family default 
.
 Generally speaking the AMS environments are more flexible, provide nicer
 spacing and more options (see the AMS documentation already mentioned).
 The only real issue with using them are potential incompatibilities between
 the AMS package and the document class you might be using, which might
 be more common than you think, especially if you got the documentclass
 files from some European journal.
 All the documentclasses supported by LyX, however, are fully compatible
 with the AMS package, so you should worry about that only if you plan to
 export your document as LaTeX and do all the configuration work manually
 on that file.
\layout Standard

For the LaTeX formula environments you have only one option, to allow page
 breaks globally and completely.
 This is done by putting the command 
\family typewriter 

\backslash 
allowdisplaybreaks
\family default 
 in your LaTeX preamble.
 For the AMS math environment you have the following options:
\layout Itemize

You can put a 
\family typewriter 

\backslash 
displaybreak
\family default 
 or a 
\family typewriter 

\backslash 
displaybreak[
\family sans 

\begin_inset Formula $n$
\end_inset 


\family typewriter 
]
\family default 
 in a specific formula in a specific position where you allow the page to
 break.
 
\begin_inset Formula $n$
\end_inset 

 is as for the 
\family typewriter 

\backslash 
linebreak
\family default 
 command.
 
\layout Itemize

You can allow page breaks in all AMS equation environments globally.
 Put the command 
\family typewriter 

\backslash 
allowdisplaybreaks[
\family sans 

\begin_inset Formula $n$
\end_inset 


\family typewriter 
]
\family default 
 in your preamble where the parameter of permissiveness 
\begin_inset Formula $n$
\end_inset 

 is between 1 (not 0!) and 4.
 Note that 
\family typewriter 

\backslash 
allowdisplaybreaks[4]
\family default 
 is identical to 
\family typewriter 

\backslash 
allowdisplaybreaks
\family default 
 and will affect the LaTeX math environments too.
\layout Standard

See some examples in appendix 
\begin_inset LatexCommand \ref{sec:Page-break-examples}

\end_inset 

.
\layout Section

About this document
\layout Standard

If you have any comments about this document I would love to hear them.
 I am especially interested in new LaTeX tips and tricks! There always seem
 to be more.
 My e-mail is 
\family typewriter 
gadykozma@hotmail.com
\family default 
.
\layout Standard

This document is in the public domain.
 Please do with it as you please.
\layout Section
\start_of_appendix 
The discretionary command
\layout Standard

The discretionary command takes three arguments, i.e.\SpecialChar ~
its general format is
 
\family typewriter 

\backslash 
discretionary{
\family default 
\shape italic 
a
\family typewriter 
\shape default 
}{
\family default 
\shape italic 
b
\family typewriter 
\shape default 
}{
\family default 
\shape italic 
c
\family typewriter 
\shape default 
}
\family default 
.
 The third argument is the text to put in the usual case, namely the line
 is not broken there.
 The first and second are for breaking lines, and appear in the end of the
 first line and the beginning of the second.
 Thus the usual hyphenation point is equivalent to 
\family typewriter 

\backslash 
discretionary{-}{}{}
\family default 
 but the German 
\family typewriter 

\backslash 
ck
\family default 
 command is equivalent to 
\family typewriter 

\backslash 
discretionary{k-}{k}{ck}
\family default 
.
 That's right, in German, sometimes when you break a ck across lines you
 want the broken text to be k-k.
\begin_inset Foot
collapsed false

\layout Standard

I don't know the first thing about German, so all this should be taken with
 a mountain of salt.
\end_inset 

 
\layout Standard

Here is a particularly freaky example.
 In the preamble, define the following:
\layout LyX-Code


\backslash 
newcommand{
\backslash 
brmul}
\newline 
{
\backslash 
discretionary{
\backslash 
mbox{$
\backslash 
,
\backslash 
cdot$}}{}{}}
\layout Standard

Next, add a formula like that 
\begin_inset Formula $f(x)=x\log x\brmul\log\log x$
\end_inset 

 (if you are reading the printed version, there is a 
\family typewriter 

\backslash 
brmul
\family default 
 between the 
\begin_inset Formula $\log x$
\end_inset 

 and the 
\begin_inset Formula $\log\log x$
\end_inset 

) and play around with the surrounding text to force it to break between
 the 
\begin_inset Formula $\log x$
\end_inset 

 and the 
\begin_inset Formula $\log\log x$
\end_inset 

.
 For example:
\layout Quote

When using, inside the line, long formulas like 
\begin_inset Formula $f(x)=x\log x\brmul\log\log x$
\end_inset 

, strange things could happen.
\layout Standard

Voilà! A multiplication sign (
\family typewriter 

\backslash 
cdot
\family default 
 is the code for 
\begin_inset Quotes eld
\end_inset 


\begin_inset Formula $\cdot$
\end_inset 


\begin_inset Quotes erd
\end_inset 


\begin_inset Foot
collapsed false

\layout Standard


\family typewriter 

\backslash 
,
\family default 
 gives the standard space before the multiplication sign.
 What about the 
\family typewriter 

\backslash 
mbox
\family default 
 and the 
\family typewriter 
$
\family default 
 signs? Weird LaTeX working mode issues.
 Don't ask me, I only fiddle until it works.
\end_inset 

) appears in the middle of the formula.
 
\layout Section


\begin_inset LatexCommand \label{sec:Page-break-examples}

\end_inset 

Page break examples
\layout Standard


\begin_inset Formula \begin{align*}
\textrm{Gauss number} & =1+2+3+4+5+6+7+8+9+10\\
 & +11+12+13+14+15+16+17+18+19+20\\
 & +21+22+23+24+25+26+27+28+29+30\\
 & \textrm{this line contains a }\mathtt{{displaybreak[3]}}\textrm{ command}\displaybreak[3]\\
 & \textrm{as you can see, in such a bad position it is not enough to force}\\
 & \textrm{a break.}\\
 & \textrm{this line contains a }\mathtt{{displaybreak}}\textrm{ command}\displaybreak\\
 & \textrm{as you can see, this command is absolute.}\\
 & +31+32+33+34+35+36+37+38+39+40\\
 & +\dotsb+100=5050\end{align*}

\end_inset 


\the_end