# Q E P C A D - QEPCAD Cell Documentation

Cell : a qepcad data structure
A list (LEVEL, CHILD, ASSIGNED, TRUTH, SAMPLE, INDX, SIGNPF, HOWTV, DEGSUB, MULSUB). Note that the constants LEVEL, CHILD, ASSIGNED, TRUTH, SAMPLE, INDX, SIGNPF, HOWTV, DEGSUB, MULSUB which define the positions of this data in the list are defined in qepcad.h.
1. LEVEL - the level of the cell.
2. CHILD - a list of qepcad Cell data structures, the children.
3. ASSIGNED - Assignment flag (for parallel execution only).
4. TRUTH - the truth value of the cell: TRUE, FALSE, or UNDET.
5. SAMPLE - a sample point data structure.
6. INDX - the index of the cell as a list.
7. SIGNPF - a list (S_1,...,S_k), where k is the LEVEL of the cell. S_i is a list (s_1,...,s_n) where n is the number of k-i+1 level projection factors, and s_j is the sign of P_(k-i+1,j) in the cell.
8. HOWTV - how the truth value was assigned, the possibilities are BYTEV = trial evaluation, BYPRP = propogation, BYEQC = equational constraint, and NOTDET = not determined.
9. DEGSUB - List of degrees of substituted projection factors.
10. MULSUB - List of multiplicities of substituted projection factors. 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.

Christopher W Brown