12.16.2 Greatest hits from previous weeks

12.16.2.1 How can I write cases with grouping braces on both left and right side, and split the condition into two lines in LaTeX?
12.16.2.2 Forcing linebreaks in \url
12.16.2.3 What does the phrase "Underfull \hbox (badness 10000) in paragraph" actually mean?
12.16.2.4 The \bar and \overline commands
12.16.2.5 Reducing font size in equation
12.16.2.6 Reduce space between enumerated items
12.16.2.7 inputenc Error: Unicode char \u8: not set up for use with LaTeX
12.16.2.1 How can I write cases with grouping braces on both left and right side, and split the condition into two lines in LaTeX?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=240868

The code I used to write 
is this one 
$$ 
X(m,n)= 
\begin{cases} 
x(n),\\ 
x(n-1)\\ 
x(n-1) 
\end{cases} 
$$ 
But I don't know how to write this one 
Also, what if I want to write this 
[math-mode] [cases]
 
asked by MaryA~ https://tex.stackexchange.com/landing/r/digest?cta=user&id=65856 Score of 208
answered by Ignasi https://tex.stackexchange.com/landing/r/digest?cta=user&id=1952 Score of 150
12.16.2.2 Forcing linebreaks in \url

https://tex.stackexchange.com/landing/r/digest?cta=question&id=3033

This question led to a new package: 
xurl 
I wish to typeset some relatively long URLs in a piece of text, and when I use \url{..}, the resulting text does not respect the margin boundaries that govern ... 
[line-breaking] [urls]
 
asked by Suresh https://tex.stackexchange.com/landing/r/digest?cta=user&id=103 Score of 375
answered by Suresh https://tex.stackexchange.com/landing/r/digest?cta=user&id=103 Score of 268
12.16.2.3 What does the phrase "Underfull \hbox (badness 10000) in paragraph" actually mean?

https://tex.stackexchange.com/landing/r/digest?cta=question&id=334246

What does the actual phrase above mean? 
[errors] [tex-core] [boxes] [paragraphs] [underfull]
 
asked by Charles Boehm https://tex.stackexchange.com/landing/r/digest?cta=user&id=116447 Score of 140
answered by David Carlisle https://tex.stackexchange.com/landing/r/digest?cta=user&id=1090 Score of 114
12.16.2.4 The \bar and \overline commands

https://tex.stackexchange.com/landing/r/digest?cta=question&id=22100

I want to represent, say, the closure of a set or the extended reals, e.g., $\bar{\mathbb{R}}$ but unfortunately this creates a bar that is much too small (horizontally) and can barely be seen. On the ... 
[stacking-symbols]
 
asked by 3Sphere https://tex.stackexchange.com/landing/r/digest?cta=user&id=6487 Score of 203
answered by Danie Els https://tex.stackexchange.com/landing/r/digest?cta=user&id=1683 Score of 111
12.16.2.5 Reducing font size in equation

https://tex.stackexchange.com/landing/r/digest?cta=question&id=60453

I wanted to type an equation in LaTeX. But it is too long to fit into one line. It involves big arrays with many columns so I cannot split it. I wanted to reduce the font size so that it can fit in ... 
[equations] [fontsize]
 
asked by sheet_ethics https://tex.stackexchange.com/landing/r/digest?cta=user&id=15765 Score of 179
12.16.2.6 Reduce space between enumerated items

https://tex.stackexchange.com/landing/r/digest?cta=question&id=6081

Background 
All book figures are set to "here definitely" (as they must come after the text that introduces them). 
Problem 
The list types (enumerated and bullet) have too much space between them. ... 
[spacing] [floats] [lists] [vertical-alignment] [positioning]
 
asked by Dave Jarvis https://tex.stackexchange.com/landing/r/digest?cta=user&id=2148 Score of 238
answered by lockstep https://tex.stackexchange.com/landing/r/digest?cta=user&id=510 Score of 32
12.16.2.7 inputenc Error: Unicode char \u8: not set up for use with LaTeX

https://tex.stackexchange.com/landing/r/digest?cta=question&id=83440

This is with ref to my previous question Package clash in multilingual report. 
\documentclass[11pt,table,a4paper]{article} 
\usepackage{lmodern} 
\usepackage[utf8]{inputenc} 
\usepackage[T1]{fontenc} 
\... 
[errors] [unicode] [languages] [cyrillic] [input-encodings]
 
asked by Manish https://tex.stackexchange.com/landing/r/digest?cta=user&id=19116 Score of 138
answered by egreg https://tex.stackexchange.com/landing/r/digest?cta=user&id=4427 Score of 102