refactor occurrence utility for common use (to be used in ctx_simplifier) per Nuno's suggestion

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/tactic/core/collect_occs.cpp

@@ -0,0 +1,97 @@
+/*++
+Copyright (c) 2011 Microsoft Corporation
+
+Module Name:
+
+    collect_cccs.cpp
+
+Abstract:
+
+    Collect variables by occurrences.
+
+Author:
+
+    Leonardo (leonardo) 2011-10-22
+
+Notes:
+
+--*/
+
+#include "ast.h"
+#include "goal.h"
+#include "hashtable.h"
+#include "collect_occs.h"
+
+bool collect_occs::visit(expr * t) {
+    if (m_visited.is_marked(t)) {
+        if (is_uninterp_const(t))
+            m_more_than_once.mark(t);
+        return true;
+    }
+    m_visited.mark(t);
+    if (is_uninterp_const(t)) {
+        m_vars.push_back(to_app(t));
+        return true;
+    }
+    if (is_var(t))
+        return true;
+    if (is_app(t) && to_app(t)->get_num_args() == 0)
+        return true;
+    m_stack.push_back(frame(t, 0));
+    return false;
+}
+    
+void collect_occs::process(expr * t) {
+    SASSERT(m_stack.empty());
+    if (visit(t))
+        return;
+    SASSERT(!m_stack.empty());
+    unsigned num;
+    expr * child;
+    while (!m_stack.empty()) {
+    start:
+        frame & fr = m_stack.back();
+        expr *  t  = fr.first;
+        switch (t->get_kind()) {
+        case AST_APP:
+            num = to_app(t)->get_num_args();
+            while (fr.second < num) {
+                child = to_app(t)->get_arg(fr.second);
+                fr.second++;
+                if (!visit(child))
+                    goto start;
+            }
+            m_stack.pop_back();
+            break;
+        case AST_QUANTIFIER:
+            // don't need to visit patterns
+            child = to_quantifier(t)->get_expr();
+            fr.second++;
+            if (!visit(child))
+                goto start;
+            m_stack.pop_back();
+            break;
+        default:
+            UNREACHABLE();
+        }
+    }
+}
+    
+    
+void collect_occs::operator()(goal const & g, obj_hashtable<expr> & r) {
+    unsigned sz = g.size();
+    for (unsigned i = 0; i < sz; i++) {
+        expr * t = g.form(i);
+        process(t);
+    }
+    
+    ptr_vector<app>::const_iterator it  = m_vars.begin();
+    ptr_vector<app>::const_iterator end = m_vars.end();
+    for (; it != end; ++it) {
+        if (m_more_than_once.is_marked(*it))
+            continue;
+        r.insert(*it);
+    }
+    m_visited.reset();
+    m_more_than_once.reset();
+}

src/tactic/core/collect_occs.h

@@ -0,0 +1,38 @@
+/*++
+Copyright (c) 2011 Microsoft Corporation
+
+Module Name:
+
+    collect_cccs.h
+
+Abstract:
+
+    Collect variables by occurrences.
+
+Author:
+
+    Leonardo (leonardo) 2011-10-22
+
+Notes:
+
+--*/
+#ifndef COLLECT_OCCS_H_
+#define COLLECT_OCCS_H_
+
+class collect_occs {
+    expr_fast_mark1  m_visited;
+    expr_fast_mark2  m_more_than_once;
+    typedef std::pair<expr *, unsigned> frame;
+    svector<frame>   m_stack;
+    ptr_vector<app>  m_vars;
+    
+    bool visit(expr * t);
+    void process(expr * t);
+    
+public:
+    
+    void operator()(goal const & g, obj_hashtable<expr> & r);
+
+};
+
+#endif

src/tactic/core/elim_uncnstr_tactic.cpp

@@ -24,6 +24,7 @@ Notes:
 #include"bv_decl_plugin.h"
 #include"array_decl_plugin.h"
 #include"datatype_decl_plugin.h"
+#include"collect_occs.h"
 #include"cooperate.h"
 #include"ast_smt2_pp.h"
 #include"ast_ll_pp.h"
@@ -32,86 +33,6 @@ class elim_uncnstr_tactic : public tactic {
 
     struct imp {
         // unconstrained vars collector
-        struct collect {
-            expr_fast_mark1  m_visited;
-            expr_fast_mark2  m_more_than_once;
-            typedef std::pair<expr *, unsigned> frame;
-            svector<frame>   m_stack;
-            ptr_vector<app>  m_vars;
-            
-            bool visit(expr * t) {
-                if (m_visited.is_marked(t)) {
-                    if (is_uninterp_const(t))
-                        m_more_than_once.mark(t);
-                    return true;
-                }
-                m_visited.mark(t);
-                if (is_uninterp_const(t)) {
-                    m_vars.push_back(to_app(t));
-                    return true;
-                }
-                if (is_var(t))
-                    return true;
-                if (is_app(t) && to_app(t)->get_num_args() == 0)
-                    return true;
-                m_stack.push_back(frame(t, 0));
-                return false;
-            }
-            
-            void process(expr * t) {
-                SASSERT(m_stack.empty());
-                if (visit(t))
-                    return;
-                SASSERT(!m_stack.empty());
-                unsigned num;
-                expr * child;
-                while (!m_stack.empty()) {
-                start:
-                    frame & fr = m_stack.back();
-                    expr *  t  = fr.first;
-                    switch (t->get_kind()) {
-                    case AST_APP:
-                        num = to_app(t)->get_num_args();
-                        while (fr.second < num) {
-                            child = to_app(t)->get_arg(fr.second);
-                            fr.second++;
-                            if (!visit(child))
-                                goto start;
-                        }
-                        m_stack.pop_back();
-                        break;
-                    case AST_QUANTIFIER:
-                        // don't need to visit patterns
-                        child = to_quantifier(t)->get_expr();
-                        fr.second++;
-                        if (!visit(child))
-                            goto start;
-                        m_stack.pop_back();
-                        break;
-                    default:
-                        UNREACHABLE();
-                    }
-                }
-            }
-            
-            void operator()(goal const & g, obj_hashtable<expr> & r) {
-                unsigned sz = g.size();
-                for (unsigned i = 0; i < sz; i++) {
-                    expr * t = g.form(i);
-                    process(t);
-                }
-                
-                ptr_vector<app>::const_iterator it  = m_vars.begin();
-                ptr_vector<app>::const_iterator end = m_vars.end();
-                for (; it != end; ++it) {
-                    if (m_more_than_once.is_marked(*it))
-                        continue;
-                    r.insert(*it);
-                }
-                m_visited.reset();
-                m_more_than_once.reset();
-            }
-        };
 
         typedef extension_model_converter mc;
 
@@ -910,7 +831,7 @@ class elim_uncnstr_tactic : public tactic {
             TRACE("elim_uncnstr_bug", g->display(tout););
             tactic_report report("elim-uncnstr-vars", *g);
             m_vars.reset();
-            collect p;
+            collect_occs p;
             p(*g, m_vars);
             if (m_vars.empty()) {
                 result.push_back(g.get());
@@ -977,7 +898,7 @@ class elim_uncnstr_tactic : public tactic {
                 m_rw->reset(); // reset cache
                 m_vars.reset(); 
                 {
-                    collect p;
+                    collect_occs p;
                     p(*g, m_vars);
                 }
                 if (m_vars.empty())