CarLaTeX
How can I have the same spacing after and before cases as after and before an usual equation, when the text is double spacing but I don't want double spacing in cases?


\documentclass{book}
\usepackage{setspace}

\usepackage{mathtools}
\usepackage{physics}
\usepackage{amssymb}
\newcommand{\punc}[1]{\,\text{#1}}
\begin{document}
\doublespacing
Something before Something before Something before Something before Something before Something before Something before Something before
$\setstretch{1} L_i =\begin{cases} 1\text{,}&\text{when }X_i \leq \xi_i\text{, with probability } p\\ 0\text{,}&\text{otherwise, with probability } 1-p\punc{.} \end{cases}$
something after something after something after something after something after
$x+y=z$
something after something after something after something after something after
\end{document}

![2020-07-29 (2).png](/image?hash=0fd6a71a47f897bbdf0a1513b9724a755f2962f29a39fee789e25349b161b4fd)
Circumscribe
You can accomplish this by setting \baselinestretch back to 1 inside the definition of the cases environment. This is a multiplier for the distance between lines in a paragraph (and also between the rows of the cases environment) and it was set to 1.667 by \doublespacing.

To patch cases, add any one of the following three snippets to your preamble (whichever you prefer):


\usepackage{etoolbox}
\AtBeginEnvironment{cases}{\renewcommand\baselinestretch{1}\selectfont}



\let\originalcases\cases
\renewcommand\cases{%
\renewcommand\baselinestretch{1}\selectfont
\originalcases
}



\edef\cases{%
\unexpanded{\renewcommand\baselinestretch{1}\selectfont}%
\unexpanded\expandafter{\cases}%
}


Note:
* The change to \baselinestretch only takes effect after \selectfont is called, which is why that command is there.
* Simply putting  \renewcommand\baselinestretch{1}\selectfont inside the cases environment doesn't work because its scope will be limited to just the first cell of the environment.
* Putting \renewcommand\baselinestretch{1}\selectfont in the equation itself (or changing \everydisplay to put it in every display equation) won't affect the spacing around the the first equation, but it will reduce the skip above (but not below) the second equation. The spacing around the first is unaffected because it has a very tall line (due to the cases) that is already placed more than the stretched \baselineskip below the previous baseline. (So don't do this.)

### Demonstration


\documentclass{book}
\usepackage{setspace}

\usepackage{mathtools}
\usepackage{physics}
\usepackage{amssymb}
\newcommand{\punc}[1]{\,\text{#1}}

\usepackage{etoolbox} %% <- added
\AtBeginEnvironment{cases}{\renewcommand\baselinestretch{1}\selectfont} %% <- added

\begin{document}
\doublespacing
Something before Something before Something before Something before Something before Something before Something before Something before
$%% <- \setstretch{1} removed L_i =\begin{cases} 1\text{,}&\text{when }X_i \leq \xi_i\text{, with probability } p\\ 0\text{,}&\text{otherwise, with probability } 1-p\punc{.} \end{cases}$
something after something after something after something after something after
$x+y=z$
something after something after something after something after something after
\end{document}


![casesspace.png](/image?hash=daae31920d2944c6d42c1151ba18e4b94a9feb11066424d6e6fea2b0b1ff2bda)

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