2 files changed, 31 insertions, 2 deletions
diff --git a/src/theory/strings/theory_strings_rewriter.cpp b/src/theory/strings/theory_strings_rewriter.cpp
index 78def9c0a..4ab81da7c 100644
--- a/src/theory/strings/theory_strings_rewriter.cpp
+++ b/src/theory/strings/theory_strings_rewriter.cpp
@@ -31,6 +31,7 @@ using namespace CVC4::theory;
 using namespace CVC4::theory::strings;
 
 Node TheoryStringsRewriter::simpleRegexpConsume( std::vector< Node >& mchildren, std::vector< Node >& children, int dir ){
+  NodeManager* nm = NodeManager::currentNM();
   unsigned tmin = dir<0 ? 0 : dir;
   unsigned tmax = dir<0 ? 1 : dir;
   //try to remove off front and back
@@ -61,7 +62,7 @@ Node TheoryStringsRewriter::simpleRegexpConsume( std::vector< Node >& mchildren,
               if( index==0 ){
                 mchildren.push_back( s );
               }else{
-                children.push_back( s );
+                children.push_back(nm->mkNode(STRING_TO_REGEXP, s));
               }
             }
             do_next = true;
diff --git a/src/theory/strings/theory_strings_rewriter.h b/src/theory/strings/theory_strings_rewriter.h
index 8befb5e0f..4c78a1945 100644
--- a/src/theory/strings/theory_strings_rewriter.h
+++ b/src/theory/strings/theory_strings_rewriter.h
@@ -28,7 +28,35 @@ namespace theory {
 namespace strings {
 
 class TheoryStringsRewriter {
-private:
+ private:
+  /** simple regular expression consume
+   *
+   * This method is called when we are rewriting a membership of the form
+   *   s1 ++ ... ++ sn in r1 ++ ... ++ rm
+   * We have that mchildren consists of the strings s1...sn, and children
+   * consists of the regular expressions r1...rm.
+   *
+   * This method tries to strip off parts of the concatenation terms. It updates
+   * the vectors such that the resulting vectors are such that the membership
+   * mchildren[n'...n''] in children[m'...m''] is equivalent to the input
+   * membership. The argument dir indicates the direction to consider, where
+   * 0 means strip off the front, 1 off the back, and < 0 off of both.
+   *
+   * If this method returns the false node, then we have inferred that the input
+   * membership is equivalent to false. Otherwise, it returns the null node.
+   *
+   * For example, given input
+   *   mchildren = { "ab", x }, children = { [["a"]], ([["cd"]])* } and dir = 0,
+   * this method updates:
+   *   mchildren = { "b", x }, children = { ("cd")* }
+   * and returns null.
+   *
+   * For example, given input
+   *   { x, "abb", x }, { [[x]], ["a"..."b"], allchar, [[y]], [[x]]} and dir=-1,
+   * this method updates:
+   *   { "b" }, { [[y]] }
+   * where [[.]] denotes str.to.re, and returns null.
+   */
   static Node simpleRegexpConsume( std::vector< Node >& mchildren, std::vector< Node >& children, int dir = -1 );
   static bool isConstRegExp( TNode t );
   static bool testConstStringInRegExp( CVC4::String &s, unsigned int index_start, TNode r );