While defining an environment <env> also defines the \<env> and \end<env> declarations, what are the circumstances where defining those declarations directly (without defining an environment) is preferable?

I see the following use where \proof and \endproof are defined separately in the informs3 document class file:

%% Use for proper proofs that end with extra space (regardless of the use
%% or non-use of \qed (=the black box)
\def\proof#1{\Trivlist\item[\hspace*{1em}\hskip\labelsep{\it #1\enskip }]\ignorespaces}

Is there any reason not to do \newenvironment{proof}[1]{...}{...} instead?

  • 2
    I'm always amazed when journal styles reinvent the wheel, making it worse than the available models. – egreg Nov 17 '18 at 16:43
  • @egreg Totally. – Fang Jing Nov 17 '18 at 17:07
  • 1
    There are pieces of code which you can use both in LaTeX as \begin{envname}..\end{envname} and, e.g., in plain-TeX (, where you neither have LaTeX 2e's \newenvironment-command nor have LaTeX 2e's environment-mechanism,) as \envname..\endenvname. – Ulrich Diez Nov 18 '18 at 11:23

\newenvironment other than checking that the name is "safe" to define does nothing different to the \def forms that you show (apart from using \long\def unless the * form is used).

Especially in older code you will often see the lower level form, going back to when it could take several minutes to load a style file and not doing the checks in often used but unchanging definitions was a useful saving.

  • I realize I can actually do \begin{proof}{Proof.} It's obvious. \end{proof}. – Fang Jing Nov 17 '18 at 17:08

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