3

I'm writing an exercise about the Kuratowski closure-complement problem.

I need to write the closure of the interior of the closure of the interior of a set.

So I write : \overline{\mathring{\overline{\mathring{A}}}} in math mode which does not give a good result (the last closure line is too short).

Can you help me?

  • You don't like how \bar{\mathring{\bar{\mathring{A}}}} looks? In any case, define symbolic names! Your code should, at least, look like \closure{\interior{\closure{\interior{A}}}}. – Manuel Sep 12 '16 at 9:46
  • For this example, it would be ok. But if you replace A by a longer set (like B(x_0, R_1)), the closure with \bar is really small. – user37238 Sep 12 '16 at 9:53
  • VERY unexpected behaviour! – Przemysław Scherwentke Sep 12 '16 at 10:10
  • @user37238 You could change your name to something more telling. You can program those commands to act differently depending on what's in their argument. – Manuel Sep 12 '16 at 10:13
  • Is it the upper \overline that is too short or the lower that is too long? Compare $\overline{\mathring{A}}\ \mathring{\overline{\mathring{A}}}$ – StefanH Sep 12 '16 at 13:05
2

Add a little bit of space before doing the last overline:

$\overline{\,\mathring{\overline{\mathring{A}}}\,}$

gives

enter image description here

1

Basically, define \closure and \interior (or shorter names if you want) and use those symbolic definitions, this way, you can program things into the macros.

\documentclass{scrartcl}
\usepackage{mathtools,amssymb}
\usepackage{xparse}

\NewDocumentCommand\closure{sm}
  {\IfBooleanTF{#1}{\overline{#2}}{\bar{#2}}}
\NewDocumentCommand\interior{sm}
  {\IfBooleanTF{#1}{?}{\mathring{#2}}{}}

\begin{document}
$\closure{\interior{\closure{\interior{A}}}}$ and $\closure*{B(x_0,R_1)}$
\end{document}

I leave an ? in a situation in which I don't know what you want (some people write it like (...)^\circ and other put an overparentheses (\overparen may be, or may be a self defined macro) and then a \mathring over the parenthesis, etc.).

On a side note, may be, depending on your documment, you might want to define something like open-ball \oB and closed-ball \cB and use like \cB(x_0,R_1) in which case it's easy to change the definition of those commands whenever you want, and you are not stuck with the raw code.

0

By inserting something to the right in the last \overline it is stretch to the end. I tried some different combinations and with

\overline{\mathring{\overline{\mathring{A}}}\phantom{.}}

I get

enter image description here

It is still just a fix and not an answer to why it behaves like it does from the beginning.

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