Frame with both optional and overlay specification can give frame-break

[blefloch]

A frame can have both an overlay specification in angle brackets and an optional argument. In that order, it works (see frame-A below). But in the other order, one gets <1> typeset, with < alone on one frame, and 1> on the next one, which is pretty puzzling.

\documentclass{beamer}
\begin{document}
\begin{frame}<1>[label=frame-A]
\end{frame}
\begin{frame}[label=frame-B]<1>
\end{frame}
\end{document}

[samcarter]

Only the first version is valid syntax, the frame environment is documented like this:

\begin{frame}<⟨overlay specification⟩>[<⟨default overlay specification⟩>][⟨options⟩]{⟨title⟩}{⟨subtitle⟩} 
⟨environment contents⟩
\end{frame}

[blefloch]

Thanks. Nevertheless the second one should not give two frames but a single frame with <1> being typeset.

[samcarter]

Even in the middle of a frame, a <1> won't be typeset as "<1>" (at least not without additional tricks)

[blefloch]

Correct, I should have added \usepackage[T1]{fontenc} to preempt this point. My surprise is with the fact that there is a frame break: < (or rather ¡) gets on one page and 1> (or rather 1¿) on the next.