redo egraph

src/util/compressed_limit_trail.h

@@ -0,0 +1,36 @@
+
+#include "util/vector.h"
+
+#pragma once
+
+class compressed_limit_trail {
+    unsigned_vector m_lim;
+    unsigned m_scopes{ 0 };
+    unsigned m_last{ 0 };
+ public:
+    
+    void push(unsigned n) { 
+        if (m_last == n)
+            m_scopes++; 
+        else {
+            for (; m_scopes > 0; --m_scopes)
+                m_lim.push_back(m_last);
+            m_last = n;
+        }
+    }
+    unsigned pop(unsigned n) {
+        SASSERT(n > 0);
+        SASSERT(m_scopes + m_lim.size() >= n);
+        if (n <= m_scopes) {
+            m_scopes -= n;
+            return m_last;
+        }
+        else {
+            n -= m_scopes;
+            m_scopes = 0;
+            m_last = m_lim[m_lim.size() - n];
+            m_lim.shrink(m_lim.size() - n);
+            return m_last;
+        }
+    }
+};