add proposed query interface

src/math/polysat/slicing.cpp

@@ -16,54 +16,21 @@ Author:
 
 /*
 
-                (x=y)
-        x  <===========  y
-       /    \           / \
-      x[7:4] x[3:0]       y[3:0]
-                <==========
-                   (by x=y)
-
-Try later:
-  Congruence closure with "virtual concat" terms
-    x = x[7:4] ++ x[3:0]
-    y = y[7:4] ++ y[3:0]
-    x[7:4] = y[7:4]
-    x[3:0] = y[3:0]
-    => x = y
-
-Recycle the z3 egraph?
-    - x = x[7:4] ++ x[3:0]
-    - Add instance euf_egraph.h
-    - What do we need from the egraph?
-        - backtracking trail to check for new equalities
-
-
-
-
-
-
-
-
-
+Example:
 (1)     x = y
 (2)     z = y[3:0]
 (3)     explain(x[3:0] == z)? should be { (1), (2) }
 
-
                     (1)
         x ========================> y
        / \                         / \          (2)
   x[7:4] x[3:0]               y[7:4] y[3:0] ===========> z
 
 
-
-
-
-
-
-
-
-
+TODO:
+- track fixed bits along with enodes
+- notify solver about equalities discovered by congruence
+- implement query functions
 
 */
 

src/math/polysat/slicing.h

@@ -253,9 +253,26 @@ namespace polysat {
         /** Extract reason for x == y */
         void explain_equal(pvar x, pvar y, sat::literal_vector& out_lits, unsigned_vector& out_vars);
 
-        // TODO:
-        // Query for a given variable v:
-        // - set of variables that share at least one slice with v (need variable, offset/width relative to v)
+        /// Example:
+        /// - assume query_var has segments 11122233 and var has segments 2224
+        /// - then the overlapping region "222" is given by width = 3, offset_var = 1, offset_query = 2.
+        /// (First version will probably only support offset 0.)
+        struct var_overlap {
+            pvar var;
+            /// number of overlapping bits
+            unsigned width;
+            /// offset of overlapping region in var
+            unsigned offset_var;
+            /// offset of overlapping region in query variable
+            unsigned offset_query;
+        };
+        using var_overlap_vector = svector<var_overlap>;
+
+        /** For a given variable v, find the set of variables that share at least one slice with v. */
+        void query_overlaps(pvar v, var_overlap_vector& out);
+
+        /** Query fixed portions of the variable v */
+        void query_fixed(pvar v, rational& mask, rational& value);
 
         std::ostream& display(std::ostream& out) const;
         std::ostream& display_tree(std::ostream& out) const;