4

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.

enter image description here

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

  • 1
    please always post complete document's not just fragments – David Carlisle Nov 5 '19 at 20:05
  • 1
    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
7

Here are two alternatives to your current setup:

  1. Put the construction inside another array.

  2. Use cases instead and a different layout.

enter image description here

\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}
| improve this answer | |
  • 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
4

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} 

enter image description here

| improve this answer | |
  • 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

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