isShellable S
The pure and nonpure cases are handled separately. If $S$ is pure, then definition III.2.1 in [St] is used. That is, $S$ is shellable if its facets can be ordered $F_1, ..., F_n$ so that the difference in the $j$th and $j1$th subcomplex has a unique minimal face, for $2 \leq j \leq n$.
If $S$ is nonpure, then definition 2.1 in [BW1] is used. That is, a simplicial complex $S$ is shellable if the facets of $S$ can be ordered $F_1, .., F_n$ such that the intersection of the faces of the first $j1$ with the faces of the $F_j$ is pure and $dim F_j  1$dimensional.






The object isShellable is a method function.