From 54ab8b50215e9a6a2f6bbabedd2605a7b24163ec Mon Sep 17 00:00:00 2001
From: Andres Noetzli <andres.noetzli@gmail.com>
Date: Fri, 17 Jan 2020 10:57:34 -0800
Subject: Initial implementation

---
 src/theory/strings/skolem_cache.cpp | 28 ++++++++++++++++++++++++++++
 src/theory/strings/skolem_cache.h   |  8 ++++++++
 2 files changed, 36 insertions(+)

diff --git a/src/theory/strings/skolem_cache.cpp b/src/theory/strings/skolem_cache.cpp
index b4e1c74ea..2991737c4 100644
--- a/src/theory/strings/skolem_cache.cpp
+++ b/src/theory/strings/skolem_cache.cpp
@@ -57,6 +57,7 @@ Node SkolemCache::mkTypedSkolemCached(
   {
     Node sk = mkTypedSkolem(tn, c);
     d_skolemCache[a][b][id] = sk;
+    d_skolemToArgs[sk] = { id, a, b };
     return sk;
   }
   return it->second;
@@ -190,6 +191,33 @@ SkolemCache::normalizeStringSkolem(SkolemId id, Node a, Node b)
       a = a[0];
     }
   }
+  else if (id == SK_SUFFIX_REM)
+  {
+    std::cout << a << d_skolemToArgs[a].a << std::endl;
+    std::cout << b << std::endl;
+    // SK_SUFFIX_REM(SK_SUFFIX_REM(a, b1), b2) ---> SK_SUFFIX_REM(a, (+ b1 b2))
+    while (d_skolemToArgs.find(a) != d_skolemToArgs.end()
+           && d_skolemToArgs[a].id == SK_SUFFIX_REM)
+    {
+      SkolemInfo info = d_skolemToArgs[a];
+      b = Rewriter::rewrite(nm->mkNode(PLUS, b, info.b));
+      a = info.a;
+      std::cout << a << std::endl;
+    }
+  }
+  else if (id == SK_PREFIX)
+  {
+    std::cout << "pfx" << a << d_skolemToArgs[a].a << std::endl;
+    std::cout << "pfx" << b << std::endl;
+    // SK_PREFIX(SK_PREFIX(a, b1), b2) ---> SK_PREFIX(a, (+ b1 b2))
+    /*
+    while (a.getKind() == kind::APPLY_UF
+           && a.getOperator() == d_skolemUfs[SK_PREFIX])
+    {
+      a = a[0];
+    }
+    */
+  }
 
   Trace("skolem-cache") << "normalizeStringSkolem end: (" << id << ", " << a
                         << ", " << b << ")" << std::endl;
diff --git a/src/theory/strings/skolem_cache.h b/src/theory/strings/skolem_cache.h
index c1e3c7214..bda9ac810 100644
--- a/src/theory/strings/skolem_cache.h
+++ b/src/theory/strings/skolem_cache.h
@@ -162,6 +162,14 @@ class SkolemCache
   std::map<Node, std::map<Node, std::map<SkolemId, Node> > > d_skolemCache;
   /** the set of all skolems we have generated */
   std::unordered_set<Node, NodeHashFunction> d_allSkolems;
+
+  struct SkolemInfo {
+    SkolemId id;
+    Node a;
+    Node b;
+  };
+
+  std::unordered_map<Node, SkolemInfo, NodeHashFunction> d_skolemToArgs;
 };
 
 }  // namespace strings
-- 
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