Reorganizing the code

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/ast/has_free_vars.cpp

@@ -0,0 +1,94 @@
+/*++
+Copyright (c) 2006 Microsoft Corporation
+
+Module Name:
+
+    has_free_vars.cpp
+
+Abstract:
+
+    <abstract>
+
+Author:
+
+    Leonardo de Moura (leonardo) 2008-06-23.
+
+Revision History:
+
+--*/
+#include"ast.h"
+#include"expr_delta_pair.h"
+#include"hashtable.h"
+
+class contains_vars {
+    typedef hashtable<expr_delta_pair, obj_hash<expr_delta_pair>, default_eq<expr_delta_pair> > cache;
+    cache                    m_cache;
+    svector<expr_delta_pair> m_todo;
+    bool                     m_contains;
+    unsigned                 m_window;
+
+    void visit(expr * n, unsigned delta, bool & visited) {
+        expr_delta_pair e(n, delta);
+        if (!m_cache.contains(e)) {
+            m_todo.push_back(e);
+            visited = false;
+        }
+    }
+
+    bool visit_children(expr * n, unsigned delta) {
+        bool visited = true;
+        unsigned dw;
+        unsigned j;
+        switch (n->get_kind()) {
+        case AST_VAR:
+            dw = m_window <= UINT_MAX - delta ? m_window + delta : UINT_MAX;
+            if (to_var(n)->get_idx() >= delta && to_var(n)->get_idx() <= dw) 
+                m_contains = true;
+            break;
+        case AST_APP:
+            j = to_app(n)->get_num_args();
+            while (j > 0) {
+                --j;
+                visit(to_app(n)->get_arg(j), delta, visited);
+            }
+            break;
+        case AST_QUANTIFIER:
+            if (delta <= UINT_MAX - to_quantifier(n)->get_num_decls()) {
+                visit(to_quantifier(n)->get_expr(), delta + to_quantifier(n)->get_num_decls(), visited);
+            }
+        break;
+        default:
+            break;
+        }
+        return visited;
+    }
+
+public:
+    // return true if n contains a variable in the range [begin, end]
+    bool operator()(expr * n, unsigned begin = 0, unsigned end = UINT_MAX) {
+        m_contains   = false;
+        m_window     = end - begin;
+        m_todo.reset();
+        m_cache.reset();
+        m_todo.push_back(expr_delta_pair(n, begin));
+        while (!m_todo.empty()) {
+            expr_delta_pair e = m_todo.back();
+            if (visit_children(e.m_node, e.m_delta)) {
+                m_cache.insert(e);
+                m_todo.pop_back();
+            }
+            if (m_contains) {
+                return true;
+            }
+        }
+        SASSERT(!m_contains);
+        return false;
+    }
+};
+
+bool has_free_vars(expr * n) {
+    contains_vars p;
+    return p(n);
+}
+
+