Can't get example of 2-cell from xy-pic reference to work

Question

I'm trying to recreate example 2 from the xypic reference manual (http://mirrors.ctan.org/macros/generic/diagrams/xypic/doc/xyrefer.pdf p.43 )

\diagram
A\ruppertwocell^f{\alpha}
\rlowertwocell_h{\beta}
\rto_(.35)g & B\\
\enddiagram

I got the first example working in the following manner with inspiration from Natural transformation arrow

\documentclass{article}
\usepackage[all,cmtip,2cell]{xy}
\UseTwocells
\xyoption{2cell}
\begin{document}
$$
\xymatrix@C+2pc{
A \rtwocell<6>^{f}_{g}{\;\;\;\alpha} & B}
$$

\end{document}

But just pasting the second example gives me

! Undefined control sequence.
l.15 \diagram

and changing \diagram to \xymatrix@C+2pc{... as above gives me:

...
(/usr/share/texlive/texmf-dist/tex/generic/xypic/xy2cell.tex
 Xy-pic option: Two-cell feature v.3.7 not reloaded) (./test2cells.aux)
<xymatrix 2x1 20> <xymatrix
! Undefined control sequence.
<argument> ...atall@ \everyentry@ A\ruppertwocell 
                                                  ^f{\alpha } \rlowertwocell...
l.19 \rto_(.35)g & B}
                     $$

What is the proper way to get this to work in xy-pic? Should I really be using the diagrams package?

Answer 1

The documentation says (just above that second diagram: "Bug: This document still uses version 2-style commmands, as described in appendix B."

To use version 2 commands like \diagram, include \xyoption{v2} or give the package option v2. And to use the half cells, use \UseAllTwoCells instead of just \UseTwocells. And please don't use $$ in LaTeX.

\documentclass{article}
\usepackage[all,v2,cmtip,2cell]{xy}
\UseAllTwocells
\begin{document}

\[
\xymatrix@C+2pc{
A \rtwocell<6>^{f}_{g}{\;\;\;\alpha} & B}
\]

\diagram
A\ruppertwocell^f{\alpha}
\rlowertwocell_h{\beta}
\rto_(.35)g & B\\
\enddiagram

\end{document}

Without the v2, the second diagram can be given as

\xymatrix@C+2pc{
A\ruppertwocell^f{\alpha}
\rlowertwocell_h{\beta}
\ar[r]_(.35)g & B}