# Extra long braces with \begin{array}[t]

the following is a snippet of a lecture note I am typing.

$\mathscr F=\left\{\{B_{\a}\}_{\a\in J}: \begin{array}[t]{rl} i) & B_{\a} \text{ are open}\\ ii) & \{B_{\a}\} \text{ is finitely inadequate}\\ iii)& I \subset J \text{ and } A_{\a}=B_{\a} \text{ whenever } \a\in I \end{array}\right\}$


where \a is a macro for \alpha. This is producing the following output.

How to curb those extra-long top ends of the braces?

• please always post complete document's not just fragments – David Carlisle Nov 5 '19 at 20:05
• why have you got [t] here? simply removing it would give better layout and more reasonable {} – David Carlisle Nov 5 '19 at 20:08
• Actually I want to start the first line of the array in the same line with \{B\}_{\a} – Subhajit Paul Nov 5 '19 at 20:12
• you could just have put that in the array in a new first column, incidentally you are using math italic for the i,ii,ii numbering which looks very weird. I'd use \text{ii)} if you can't use an enumerate enviornment. – David Carlisle Nov 5 '19 at 20:16

Here are two alternatives to your current setup:

1. Put the construction inside another array.

2. Use cases instead and a different layout.

\documentclass{article}

\usepackage{amsmath,mathrsfs}

\begin{document}

$\mathscr F = \left\{ \begin{array}{@{} l @{}} \{B_{\alpha}\}_{\alpha\in J}: \begin{array}[t]{r @{~} l} \textit{i}) & B_{\alpha} \text{ are open}\\ \textit{ii}) & \{B_{\alpha}\} \text{ is finitely inadequate}\\ \textit{iii}) & I \subset J \text{ and } A_{\alpha}=B_{\alpha} \text{ whenever } \alpha\in I \end{array} \end{array} \right\}$

$\mathscr F = \{B_{\alpha}\}_{\alpha\in J}: \begin{cases} \textit{i}) & B_{\alpha} \text{ are open}\\ \textit{ii}) & \{B_{\alpha}\} \text{ is finitely inadequate}\\ \textit{iii}) & I \subset J \text{ and } A_{\alpha}=B_{\alpha} \text{ whenever } \alpha\in I \end{cases}$

\end{document}

• Can you please enlighten me what role do @{} and @{~} play here? – Subhajit Paul Nov 5 '19 at 19:53
• both of these break the top alignment, the first is essentially identical to simply leaving the [t] off the array in the question. (although actually lowering the braces wiile preserving teh top alignment (with delarray) would look weird, I don't think I'll post that answer:-) – David Carlisle Nov 5 '19 at 20:05
• @SubhajitPaul: @{} as part of the column specification removes the column separation. @{~} removes the column separation and inserts a tie ~ instead. – Werner Nov 5 '19 at 20:13

I propose two other variants, built upon Bmatrix , \parbox and an inline enumerate environment:

\documentclass{article}

\usepackage{amsmath,mathrsfs}
\usepackage[inline]{enumitem}

\begin{document}

$\mathscr F = \begin{Bmatrix} \{B_{\alpha}\}_{\alpha\in J}:\: \parbox{75mm}{% \begin{enumerate*}[label = \roman*) , itemjoin ={; \enspace}] \item  B_{\alpha}  are open \item  \{B_{\alpha}\}  is finitely inadequate \item I \subset J  and  A_{\alpha}=B_{\alpha}  whenever  \alpha\in I . \end{enumerate*}} \end{Bmatrix}$

$\mathscr F = \begin{Bmatrix} \{B_{\alpha}\}_{\alpha\in J}:\; \parbox[t]{75mm}{% \begin{enumerate*}[label = \roman*) , itemjoin ={; \enspace}] \item  B_{\alpha}  are open \item  \{B_{\alpha}\}  is finitely inadequate \item I \subset J  and  A_{\alpha}=B_{\alpha}  whenever \alpha\in I. \end{enumerate*}} \end{Bmatrix}$

\end{document}


• ooh an inline list, not sure I would have thought of that, I quite like the second one (+1) (not so sure about the first) – David Carlisle Nov 5 '19 at 21:32
• @DavidCarlisle: the first version, for me, would be nicer with a vertical rule. – Bernard Nov 5 '19 at 21:39