The following definition of \sp throws a "Missing $" error, I cant see any possible reason for this! Could somebody please explain?
\documentclass{amsart}
\providecommand{\sp}[1][10]{\par \vspace{#1 pt} \noindent\ignorespaces}
\begin{document}
line
\sp
line
\end{document}
I don't know how to accept the answer in a comment, but if I knew I would accept @HenriMenke's comment, which is clearly the best practice. On the other hand, while I should never have used \sp in the first place, I've been using it for years and it's hard to change. The following does work, i.e., overrides the default definition of \sp
\let\sp\undefined
\newcommand{\sp}[1][10]{\par\vspace{#1pt}\noindent\ignorespaces}
bad practice as it is.
\documentclass{amsart}twice?? – skpblack Jul 18 '17 at 03:27\spis the superscript operator and\providecommandwill not override the original definition. – Henri Menke Jul 18 '17 at 03:37\spfor other. (\spalready exists) – skpblack Jul 18 '17 at 03:43\providecommandhas its uses, I'd discourage using it for personal commands: use\newcommand, which would warn you in case you're trying to define an existing command. – egreg Jul 18 '17 at 07:49\newcommand,\renewcommand, and\providecommanddo, and how do they differ? – Werner Jul 30 '17 at 08:26