3

I don't seem to understand how spacing in environments works: Look at

\documentclass{article}

\usepackage{amsthm}

\newenvironment{myproof}{\par\noindent\textit{Proof.}}{\qed}
\newenvironment{myproof2}[1][Proof]{\par\noindent\textit{#1.} }{\qed}
\newenvironment{myproof3}[1][Proof]{\par\noindent\textit{#1.}}{\qed}

\begin{document}
    \begin{proof}
        I
    \end{proof}

    \begin{myproof}
        I
    \end{myproof}

    \begin{myproof2}
        I
    \end{myproof2}

    \begin{myproof3}
        I
    \end{myproof3}
\end{document}

leading to

enter image description here

Why don't I have to include a space manually if I don't use an option, but have to use one if I include the capability of optional arguments?

Why are my spaces smaller than those of amsthm? I would like to have them as in the original proof environment.

  • Why not using the original? – egreg Apr 13 '18 at 8:11
  • @egreg I want to create a proof-of-claim-inside-a-proof environment with an alternative qed symbol, less vertical spacing, etc. – John Dorian Apr 13 '18 at 8:13
2

Tell LaTeX to ignore subsequent spaces:

\documentclass{article}

\usepackage{amsthm}

\usepackage[nopar]{lipsum}

\newcommand{\closedbox}{%
  \makebox[0.77778em]{\rule{0.675em}{0.675em}}%
}

\newenvironment{innerproof}[1][Proof]
  {\par\addvspace{\smallskipamount}%
   \renewcommand{\qedsymbol}{\closedbox}%
   \noindent\textit{#1.}\hspace{\labelsep}\ignorespaces}
  {\qed\par\addvspace{\smallskipamount}}

\begin{document}

\openbox\closedbox

\begin{proof}
\lipsum[4]
\begin{innerproof}
\lipsum[5]
\end{innerproof}
\lipsum[6]
\begin{innerproof}[Proof of claim]
\lipsum[5]
\end{innerproof}
\lipsum[6]
\end{proof}

\end{document}

enter image description here

| improve this answer | |
  • Thank you very much. So the correct length of the space was \labelsep. Btw I was not aware that \renewcommand does not have a global effect if put inside {}. Learned something again :-) – John Dorian Apr 13 '18 at 8:38
  • This is of course not relevant to your proof of concept, but I think your black square is bigger than the original \qedsymbol. – John Dorian Apr 13 '18 at 8:39
  • @JohnDorian Fixed the size. – egreg Apr 13 '18 at 10:58

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