a modern C++ library for the manipulation of Boolean functions

An even more exotic class of functions
The conj algorithm takes a set of variables V =
v1, v2, . . . vn as its argument and
builds the ROBDD for the Boolean function that evaluates to false if and only if one
and only one variable in V is false. This function can be viewed as:
(v0 ⇐= v1 ∧v2 ∧. . .∧vn)∧(v1 ⇐= v0 ∧v2 ∧. . .∧vn)∧. . .∧(vn ⇐= v0 ∧v1 ∧. . .∧vn−1)
Since we must conjunct a set of clauses, we start by building the ROBDD for the first
clause, then we build the ROBDD for the second one and conjunct it with the first one
using and_ite, then we conjunct the result with the ROBDD for the third one and so on.
The only problem we still have to solve is how to build the ROBDD for a Boolean
function of type v ⇐= t1 ∧ t2 ∧ . . . ∧ tn. As with the two previous algorithms, the solution
is trivial when the implied variable is greater than all the others: the result is simply a
ROBDD whose root is labeled with v, has 1 as its true successor and has the ROBDD
for ¬t1 ∨ ¬t2 ∨ . . . ∨ ¬tn as its false successor. So we start as usual by considering only
the greater variables and building the corresponding ROBDD; afterwards we handle the
smaller variables as shown in Algorithm 21.
3.2 ROBDD algorithms 32