5

I want display how a function assigns a very long value to an ordered pair. I am not sure where the \mapsto arrow should be placed and how much the second element in the ordered pair should be indented.

Here is a MWE.

\documentclass[paper=letter,fontsize=12pt]{scrreprt}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathtools}

\begin{document}
\begin{equation}
        \Psi_{G}(s, t) \longmapsto \begin{aligned}
            &\big( \vee \!\{ m \in M_{G} \colon \Phi_{G}^{s}(m) - \Phi_{G}^{t}(m) > i \}, \\
            &\qquad \qquad \vee \!\{ m \in M_{G} \colon \Phi_{G}^{t}(m) - \Phi_{G}^{s}(m) > i \} \big) \text{.}
        \end{aligned}
    \end{equation}
\end{document}

Here is what the equation looks like.

enter image description here

3 Answers 3

4

Here's my proposal: the \mapsto should be level with the opening parenthesis.

\documentclass[paper=letter,fontsize=12pt]{scrreprt}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathtools}

\newcommand{\tbigvee}{\mathop{\mathchoice{\textstyle\bigvee}{\bigvee}{\bigvee}{\bigvee}}}

\begin{document}

\begin{equation}
\begin{aligned}
  \Psi_{G}(s, t) \mapsto {}
  &\bigl( \tbigvee \{ m \in M_{G} : \Phi_{G}^{s}(m) - \Phi_{G}^{t}(m) > i \}, \\
  &\qquad \tbigvee \{ m \in M_{G} : \Phi_{G}^{t}(m) - \Phi_{G}^{s}(m) > i \}
  \bigr).
\end{aligned}
\end{equation}

\end{document}

enter image description here

  1. \big( and \big) are wrong, use \bigl( and \bigr)
  2. \longmapsto is too long (but this is personal opinion)
  3. \vee is not the right symbol to denote the supremum of a set; in this context, however, \bigvee would be too big and so I provided a reduced version
  4. \colon is not the right symbol; use : to get good spacing around it
4
  • I've looked at the spacing around "\colon" in my version and ":" in your version and see no difference. Perhaps there are cases where there are differences but this is not one of them.
    – Jay
    Commented Dec 9, 2022 at 13:57
  • @Jay I do see a difference: the space on the left of the colon is shorter with \colon than with :
    – egreg
    Commented Dec 9, 2022 at 14:06
  • I agree that \colon and : give different spacing, but to me \colon is the superior choice: it emphasizes the asymmetry in the roles of the expressions to the left and right. I believe \colon is Knuth's choice as well. Commented Dec 9, 2022 at 18:27
  • @GregMartin I don't think so. Knuth's colon is different from the \colon of amsmath. And Knuth uses : or \mid in the TeXbook (bottom of page 174). Anyway, be consistent. I'd probably do \newcommand{\sst}{\colon} and use \sst for the separator, so I could change the appearance of all set denotations by modifying the definition.
    – egreg
    Commented Dec 9, 2022 at 18:38
5

Is one of the following two "looks" what you're looking for? [pun intended]

enter image description here

\documentclass[paper=letter,fontsize=12pt]{scrreprt}
%\usepackage[utf8]{inputenc} % that's the default nowadays
%\usepackage{amsmath} % amsmath is loaded automatically mathtools
\usepackage{amssymb}
\usepackage{mathtools} % for 'pmatrix*' env.
\usepackage{relsize}
\newcommand\Vee{\mathlarger{\vee}} % 20% linear enlargement

\begin{document}
\setcounter{chapter}{1} % just for this example

\begin{equation}
\Psi_{G}(s, t) \longmapsto 
\begin{aligned}[t]
\bigl(&\Vee \{ m \in M_{G} : \Phi_{G}^{s}(m) - \Phi_{G}^{t}(m) > i \}, \\
      &\Vee \{ m \in M_{G} : \Phi_{G}^{t}(m) - \Phi_{G}^{s}(m) > i \} \bigr) 
\end{aligned}
\end{equation}

\begin{equation}
\Psi_{G}(s, t) \longmapsto 
\begin{pmatrix*}[l]
   \Vee \{ m \in M_{G} : \Phi_{G}^{s}(m) - \Phi_{G}^{t}(m) > i \}, \\
   \Vee \{ m \in M_{G} : \Phi_{G}^{t}(m) - \Phi_{G}^{s}(m) > i \} 
\end{pmatrix*}
\end{equation}

\end{document}
1
  • I like the top version better. To me the bottom version looks too much like a matrix. You like the other two currently visible answers are using ":", "\bigl(", and "\bigr". I can take a hint.
    – Jay
    Commented Dec 9, 2022 at 13:45
4

Perhaps giving each supremum a name would make this easier to read:

enter image description here

\documentclass[paper=letter,fontsize=12pt]{scrreprt}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathtools}

\begin{document}

For each $s$ and $t$, define
\begin{align*}
S(s,t)&=\bigvee \bigl\{ m \in M_{G} : \Phi_{G}^{s}(m) - \Phi_{G}^{t}(m) > i \bigr\} \\
\shortintertext{and}
T(s,t)&=\bigvee \bigl\{ m \in M_{G} : \Phi_{G}^{t}(m) - \Phi_{G}^{s}(m) > i \bigr\}.
\end{align*}
Then let 
\begin{equation}
    \Psi_{G}(s, t) \longmapsto \bigl(S(s,t),T(s,t)\bigr).
\end{equation}
\end{document}

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