Large Curly brackets

So I'm new to LaTeX and I have a problem. I want to type large curly brackets. My document type is article To be more specific, here's what I want to type:

• Welcome to TeX.SE. Are you familiar with \left\{ and \right\}?
– Mico
Mar 18, 2020 at 20:40
• Are you sure you should have two closing braces at the end? Mar 18, 2020 at 20:45
• @hesham: the inner braces do not denote a set, but a series of three conditions, so the inner left brace is enough (just like in the cases environment). Mar 18, 2020 at 21:21
• @hesham Hhh don't worry I realized that moments ago. I have fixed it I accepted the very first answer. Mar 18, 2020 at 21:27
• Yes, but it is not used in the context of a new set.. Please take a look at mu=y updated answer: I've added what I have in mind. Mar 18, 2020 at 21:38

Does this go in the right direction?

\documentclass[fleqn]{article}
\usepackage{amsmath,amsfonts}
\usepackage{newtxtext,newtxmath}
\begin{document}
$\tau=\left\{ G\subset\overline{\mathfrak{R}}/ \forall x\in G, \left\{\begin{array}{@{}l@{\ /\ }l@{,\ }l@{}} \exists a,b\in\mathfrak{R} & x\in [a,b\mathclose[\subset G&x\ne\pm\infty\\ \exists b\in\mathfrak{R} & x\in [-\infty,b[\subset G&x=-\infty\\ \exists a\in\mathfrak{R} & x\in \mathopen]a,\infty]\subset G&x=+\infty \end{array}\right\} \right\}$
\end{document}


(I am not sure I understand the notation, though.) EDIT: Added \mathopen and \mathclose, as suggested by @egreg.)

• Thanks this works perfectly fine. Mar 18, 2020 at 20:57
• x\in[-\infty,b\mathclose[ or the spacing goes awry. Similarly, in the third line, x\in\mathopen]a,+\infty] (the OP uses +\infty, but the main thing is \mathopen). The first line should have x\in\mathopen]a,b\mathclose[ Mar 18, 2020 at 21:56
• @egreg Mille grazie! I agree, of course. (I must admit that I do not fully grasp the meaning of /\forall\in G and the full construction. If it is what I think it could be I'd probably typeset it in a different way.)
– user194703
Mar 18, 2020 at 22:27
• That's not the best way to describe the standard topology on the extended real line. Too many symbols make it very difficult to understand. By the way, looking at the OP's picture, the top line should be x\in\mathopen]a,b\mathclose[ Mar 18, 2020 at 22:31

Yet another solution, in two variants:

\documentclass{article}
\usepackage{array}
\usepackage{mathtools}
\DeclarePairedDelimiter{\set} \{ \}

\DeclareFontFamily{U}{mathx}{\hyphenchar\font45}
\DeclareFontShape{U}{mathx}{m}{n}{
<-6> mathx5 <6-7> mathx6 <7-8> mathx7
<8-9> mathx8 <9-10> mathx9
<10-12> mathx10 <12-> mathx12
}{}
\DeclareSymbolFont{mathx}{U}{mathx}{m}{n}
\DeclareFontSubstitution{U}{mathx}{m}{n}
\DeclareMathAccent{\widebar}{0}{mathx}{"73}

\begin{document}

$\tau = \set*{% G \subset \widebar{\Re}\bigm / \forall X\in G, \begin{Bmatrix} \begin{array}{@{}l!{/}l@{\:}l@{}} \exists a, b \in\Re & x\in{]a, b[}\subset G, &x\ne \pm\infty \\ \exists b \in\Re & x\in{[-\infty, b[}\subset G, &x = -\infty \\ \exists ab \in\Re & x\in {]a, + \infty]} \subset G, &x = + \infty \end{array} \end{Bmatrix}}%$%

$\tau = \set*{% G \subset \widebar{\Re}\bigm / \forall X\in G, \begin{cases} \begin{array}{@{}l!{/}l@{\:}l@{}} \exists a, b \in\Re & x\in{]a, b[}\subset G, &x\ne \pm\infty \\ \exists b \in\Re & x\in{[-\infty, b[}\subset G, &x = -\infty \\ \exists ab \in\Re & x\in {]a, + \infty]} \subset G, &x = + \infty \end{array} \end{cases}}%$%

\end{document}


Or maybe something like this? (Note that I've gone ahead and inserted commas as separators in the interval expressions.)

\documentclass{article}
\usepackage{amssymb} % for "\mathfrak" macro
\newcommand\R{\mathfrak{R}}

\begin{document}
$\tau= \left\{ G\subset\overline{\R} \mid \forall x\in G, \left\{ \begin{array}{@{}l@{}} \exists a,b\in\R \mid x\in\mathopen{]}a,b\mathclose{[} \subset G,\ x\ne\pm\infty \\ \exists b\in\R \mid [-\infty,b\mathclose{[} \subset G,\ x=-\infty \\ \exists a\in\R \mid \mathopen{]}a,+\infty] \subset G,\ x=+\infty \end{array} \right\} \right\}$
\end{document}