How can I format the following very long set description? Ideally, it should split into two lines.
The general structure of the set description is:
\{f(x) :| x \in S |: P(x)\}
This is a non-standard set notation, which means: the set obtained by running through all the x's in the set S, choosing only those x's that satisfy the predicate P, and then applying the function f to the selected x's and collecting the results into a set.
Additionally, the left part of the set below is of the form a \mapsto b (b being the cases structure). This is simply syntactic sugar for the ordered pair (a,b)
\documentclass{article}
\usepackage{amsmath}
\begin{document}
$$
\left\{\ddot{\mathbf{A}}_{d(\Omega;\dot{E})}(T.d)[i] \mapsto f_{d(\Omega;\dot{E})}^T(l,u)[i]\ :\!|\ i \in [1..T.d.n]\ |\!:\ F_{d(\Omega;\dot{E})}^T[i-1] \leq u \wedge F_{d(\Omega;\dot{E})}^T[i] \geq l\right\}
$$
\end{document}
Here the typeset result is seen in context. It extends into the right margin almost all the way to the right edge of the page.
I've tried using \split and \multlined as per egreg's suggestion in a comment below.
SPLIT
\begin{split}
\left\{\ddot{\mathbf{A}}_{d(\Omega;\dot{E})}(T.d)[i] \mapsto f_{d(\Omega;\dot{E})}^T(l,u)[i]\ &:\!|\ i \in [1..T.d.n]\\
&|\!:\ F_{d(\Omega;\dot{E})}^T[i-1] \leq u \wedge F_{d(\Omega;\dot{E})}^T[i] \geq l\right\}
\end{split}
It produces the following error message:
Extra }, or forgotten \right.
MULTLINED
\begin{multlined}[t]
\left\{\ddot{\mathbf{A}}_{d(\Omega;\dot{E})}(T.d)[i] \mapsto f_{d(\Omega;\dot{E})}^T(l,u)[i]\ :\!|\ i \in [1..T.d.n]\\
|\!:\ F_{d(\Omega;\dot{E})}^T[i-1] \leq u \wedge F_{d(\Omega;\dot{E})}^T[i] \geq l\right\}
\end{multlined}
It produces the following error message:
Missing \right. inserted.

$$..$$in LaTeX. – GuM Mar 27 '18 at 19:53splitormultlined. Where to break is your decision. Anyway, inputting:|and|:yields a different result than your picture. And\dotois undefined. – egreg Mar 28 '18 at 06:48