\cdbalgorithm{pop}{}

Remove the last step of the indicated expression
history. 
\begin{screen}{1,2,4}
A (B + C);
@distribute!(%);
A B + A C;
@pop(%);
A (B + C);
\end{screen}
This only works if history keeping was not turned off with
the \subsprop{KeepHistory} property.

\cdbseealgo{amnesia}
\cdbseeprop{KeepHistory}
