De Morgan dual of fwd slicing vs. bwd slicing on opposite graph

[Roly Perera]

We want to contrast $(\triangleright_{G})^{\circ}$ (De Morgan dual of fwd slicing) with equivalent $\triangleleft_{G^{\mathsf{op}}}$ (bwd slicing on opposite graph). It's a bit hard to notate these things because of all the equivalences, so here we should understand $\triangleright$ to mean our concrete forward-slicing algorithm, and $\triangleleft$ to mean our concrete backward-slicing algorithm.

Also look at $(\triangleleft_{G^{\mathsf{op}}})^{\circ}$ (Forward slicing as the De Morgan dual of backward slicing on the opposite graph).

See also:

• #780

[Roly Perera]

@JosephBond Something to consider for Performance section. (Maybe third subsection?)