How to write two *unaligned* multi-line braces on both sides

Question

I have a theorem which is about some 4 conditions, 3 of which are equivalent in one case, and some other three are equivalent in some other case, hence I would like to typeset something like this:

\begin{align*}
   equivalent if B -{ condition (1) \        
                    { condition (2) \\     }-  equivalent if A
                    { condition (3) \\     }
                      condition (4) \      }
\end{align*}

I can do one brace or the other, or both if one's scope extended the other or was disjoint from the other's. But what can I do in this case? Is it possible without hacking too much?

What about non-mathmode alternatives?

Answer 1

\documentclass{article}
\usepackage{amsmath}
\usepackage{stackengine}
\setstackEOL{\#}
\setstackgap{L}{.7\baselineskip}
\begin{document}
\begin{equation*}
\begin{aligned}
   &condition (1) &\\       
   equivalent\ if\ B - \smash{\left\{\Centerstack{\#\#\#}\right.} \, &condition (2) &\\
   &condition (3) &\!\!\!\smash{\left\}\Centerstack{\#\#\#}\right.}-  equivalent\ if\ A\\     
   & condition (4) &    
\end{aligned}
\end{equation*}
\end{document}

As a follow up, to make the conditions centered with respect to each other, I could use an array environment (or tabular for text mode), rather than aligned. Also, because array and tabular environments redefine \baselineskip, one has to set the stackgap to an explicit point value, rather than defining it in terms of \baselineskip.

\documentclass{article}
\usepackage{amsmath}
\usepackage{stackengine}
\setstackEOL{\#}
\setstackgap{L}{10pt}
\begin{document}

\begin{equation*}
\arraycolsep=.5ex
\renewcommand\arraystretch{1.2}
\begin{array}{rcl}
   &condition\ (1) &\\       
   equivalent\ if\ B - \smash{\left\{\Centerstack{\#\#\#}\right.} &condition\ (2) &\\
   &condition\ (3) &\smash{\left\}\Centerstack{\#\#\#}\right.}-  equivalent\ if\ A\\     
   & centered\ condition\ (4) &    
\end{array}
\end{equation*}

{\centering\renewcommand\arraystretch{1.2}
\tabcolsep=.5ex
\begin{tabular}{rcl}
   &condition\ (1) &\\       
   equivalent\ if\ B - $\smash{\left\{\Centerstack{\#\#\#}\right.}$ &condition\ (2) &\\
   &condition\ (3) &$\smash{\left\}\Centerstack{\#\#\#}\right.}$-  equivalent\ if\ A\\     
   & centered\ condition\ (4) &    
\end{tabular}\par}
\end{document}

Answer 2

This is a job for \valign! Although I don't think this will help readers much.

\documentclass{article}

\begin{document}

\valign{#\cr
  \vbox{\hbox{%
    Equivalent if $A$
    $\left\{\vphantom{\begin{tabular}{c} A\\B\\C\end{tabular}}\right.$%
  }}
  \vfill\cr
  \hbox{\begin{tabular}{@{}c@{}}
  Condition (1) \\
  Condition (2) \\
  Condition (3) \\
  Condition (4)
  \end{tabular}}\cr
  \vfill
  \vbox{\hbox{%
    $\left.\vphantom{\begin{tabular}{c} A\\B\\C\end{tabular}}\right\}$
    Equivalent if $B$%
  }}\cr
}

\end{document}

Answer 3

Here's a solution that uses only arrays to align the three parts. The outermost array, which is set up to have three columns, serves to "house" the three horizontal parts. Each horizontal part consists of four rows, but some of the cells in the left-hand and right-hand parts -- which are constructed as nested arrays, each consisting of a single column -- are empty. The instruction \null is used to create empty cells.

The middle part is currently set up as a tabular rather than as an array since it would appear to contain mostly text. If that's not correct, i.e., if it's supposed to contain mostly math as well, you could could use an array environment for the middle parts as well. Conversely, if the left-hand and right-hand parts are to contain mostly text, you may want to use tabulars instead of arrays to define their layout.

\documentclass{article}
\usepackage{amsmath} %% for "\text" macro
\begin{document}
\[
\begin{array}{c@{}c@{}c}  %% outermost array: 3 centered columns
\begin{array}{c} \left. \begin{array}{@{}c}  %% a pair of nested arrays
  \null \\ \text{equivalent if $B$} \\ \null
\end{array} \right\{ \\ \null \end{array}
&
\begin{tabular}{c}
Condition (1)\\
Condition (2)\\
Condition (3)\\
Condition (4)\\
\end{tabular}
&
\begin{array}{c}  %% another pair of nested arrays
\null \\
\left\} \begin{array}{c@{}}%
  \null \\ \text{equivalent if $A$} \\ \null
\end{array} \right. \end{array}
\end{array}
\]
\end{document}