A PCAD (or "Pruned CAD") is a data-structure representing a simplification of an existing QEPCAD CAD structure.

A PCAD cell C is a list of 4 objects, (c,P,I,T), defined as follows:

  1. c is a QEPCAD cell structure. The cell represented by c is contained in the cell represented by C, and c is a section if and only if C is a section.

  2. P is NULL if C is the root cell, and the parent PCAD cell of C otherwise.

  3. I is defined as follows: I = 0 if C is the root, and otherwise C is the Ith cell in the stack over P, i.e. the stack index of C.

  4. T if C is a leaf cell, then T is C's truth value. Otherwise, T is a list of C's children.

This structure is "defined" in the file pcad.h (coarsecad.h in my private copy), which defines the constants: SC_REP, SC_PAR, SC_INX, and SC_CDTV, used with LELTI to access c, P, I, and T respectively.

Christopher W. Brown
Last modified: Fri Jan 22 16:19:25 EST 1999