Cells

A cell is represented by a list of length 10.  Each list element
has a name to which is assigned as constant value its position
in the list.  Following are the names, list positions and brief
descriptions of the elements.  (The names and their values
can be found in the file qepcad.h in the source directory.)

LEVEL      1   The level of the cell.
CHILD      2   List of the children cells of the cell.
ASSIGNED   3   Assignment flag (for parallel execution only).
TRUTH      4   Truth value of the cell.
SAMPLE     5   Sample point for the cell.
INDX       6   Cell index (represented as a list).
SIGNPF     7   Signature of the projection factors in the cell.
HOWTV      8   How the truth value of the cell was determined.
DEGSUB     9   List of degrees of substituted projection factors.
MULSUB     10  List of multiplicities of substituted projection factors.

The signature of the projection factors in a cell of level k is a
list whose i-th element is the (constant) sign of the i-th
level k projection factor (P_k,i) in the cell.  The list of
multiplicities of substituted projection factors is a list
((i_1,e_1),...,(i_n,e_n)), n >= 0, with i_1 < i_2 < ... < i_n
and each e_j > 0 where the i_j are the second indices of all
k-level projection factors which are zero in the cell and e_j
is the multiplicity of the zero.  This is a null list for
each sector, a non-null list for each section.