diff --git a/src/library/simplifier/rewrite_rule_set.cpp b/src/library/simplifier/rewrite_rule_set.cpp
new file mode 100644
index 000000000..7174f87d4
--- /dev/null
+++ b/src/library/simplifier/rewrite_rule_set.cpp
@@ -0,0 +1,121 @@
+/*
+Copyright (c) 2014 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#include "util/splay_tree.h"
+#include "util/list_fn.h"
+#include "util/sstream.h"
+#include "kernel/environment.h"
+#include "library/equality.h"
+#include "library/simplifier/ceq.h"
+#include "library/simplifier/rewrite_rule_set.h"
+
+namespace lean {
+/**
+   \brief Actual implementation of the \c rewrite_rule_set class.
+*/
+class rewrite_rule_set::imp {
+    typedef splay_tree<name, name_quick_cmp> name_set;
+    struct rewrite_rule {
+        name m_id;
+        expr m_lhs;
+        expr m_ceq;
+        expr m_proof;
+        bool m_is_permutation;
+        rewrite_rule(name const & id, expr const & lhs, expr const & ceq, expr const & proof, bool is_permutation):
+            m_id(id), m_lhs(lhs), m_ceq(ceq), m_proof(proof), m_is_permutation(is_permutation) {}
+    };
+    ro_environment::weak_ref m_env;
+    list<rewrite_rule>       m_rule_set; // TODO(Leo): use better data-structure, e.g., discrimination trees
+    name_set                 m_disabled_rules;
+
+public:
+    imp(ro_environment const & env):m_env(env.to_weak_ref()) {}
+
+    void insert(name const & id, expr const & th, expr const & proof) {
+        ro_environment env(m_env);
+        for (auto const & p : to_ceqs(env, th, proof)) {
+            expr const & ceq   = p.first;
+            expr const & proof = p.second;
+            bool is_perm       = is_permutation_ceq(ceq);
+            expr lhs = ceq;
+            while (is_pi(lhs)) {
+                lhs = abst_body(lhs);
+            }
+            lean_assert(is_equality(lhs));
+            lhs = arg(lhs, num_args(lhs) - 2);
+            m_rule_set.emplace_front(id, lhs, ceq, proof, is_perm);
+        }
+    }
+
+    void insert(name const & th_name) {
+        ro_environment env(m_env);
+        auto obj = env->find_object(th_name);
+        if (obj && (obj->is_theorem() || obj->is_axiom())) {
+            insert(th_name, obj->get_type(), mk_constant(th_name));
+        } else {
+            throw exception(sstream() << "'" << th_name << "' is not a theorem nor an axiom");
+        }
+    }
+
+    bool enabled(rewrite_rule const & rule) const {
+        return !m_disabled_rules.contains(rule.m_id);
+    }
+
+    bool enabled(name const & id) const {
+        return !m_disabled_rules.contains(id);
+    }
+
+    void enable(name const & id, bool f) {
+        if (f)
+            m_disabled_rules.erase(id);
+        else
+            m_disabled_rules.insert(id);
+    }
+
+    void for_each_match_candidate(expr const &, match_fn const & fn) const {
+        auto l = m_rule_set;
+        for (auto const & rule : l) {
+            if (enabled(rule) && fn(rule.m_lhs, rule.m_ceq, rule.m_is_permutation, rule.m_proof))
+                return;
+        }
+    }
+
+    void for_each(visit_fn const & fn) const {
+        auto l = m_rule_set;
+        for (auto const & rule : l) {
+            fn(rule.m_id, rule.m_ceq, rule.m_proof, enabled(rule));
+        }
+    }
+
+    format pp(formatter const & fmt, options const & opts) const {
+        format r;
+        bool first = true;
+        unsigned indent = get_pp_indent(opts);
+        for_each([&](name const & name, expr const & ceq, expr const &, bool enabled) {
+                if (first)
+                    first = false;
+                else
+                    r += line();
+                r += format(name);
+                if (!enabled)
+                    r += format(" [disabled]");
+                r += format{space(), colon(), space()};
+                r += nest(indent, fmt(ceq, opts));
+            });
+        return r;
+    }
+};
+rewrite_rule_set::rewrite_rule_set(ro_environment const & env):m_ptr(new imp(env)) {}
+rewrite_rule_set::rewrite_rule_set(rewrite_rule_set const & rs):m_ptr(new imp(*(rs.m_ptr))) {}
+rewrite_rule_set::~rewrite_rule_set() {}
+void rewrite_rule_set::insert(name const & id, expr const & th, expr const & proof) { m_ptr->insert(id, th, proof); }
+void rewrite_rule_set::insert(name const & th_name) { m_ptr->insert(th_name); }
+bool rewrite_rule_set::enabled(name const & id) const { return m_ptr->enabled(id); }
+void rewrite_rule_set::enable(name const & id, bool f) { m_ptr->enable(id, f); }
+void rewrite_rule_set::for_each_match_candidate(expr const & e, match_fn const & fn) { m_ptr->for_each_match_candidate(e, fn); }
+void rewrite_rule_set::for_each(visit_fn const & fn) { m_ptr->for_each(fn); }
+format rewrite_rule_set::pp(formatter const & fmt, options const & opts) const { return m_ptr->pp(fmt, opts); }
+}
diff --git a/src/library/simplifier/rewrite_rule_set.h b/src/library/simplifier/rewrite_rule_set.h
new file mode 100644
index 000000000..da35158ee
--- /dev/null
+++ b/src/library/simplifier/rewrite_rule_set.h
@@ -0,0 +1,68 @@
+/*
+Copyright (c) 2014 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+
+Author: Leonardo de Moura
+*/
+#pragma once
+#include <memory>
+#include <functional>
+#include "kernel/environment.h"
+#include "kernel/formatter.h"
+
+namespace lean {
+class rewrite_rule_set {
+    class imp;
+    std::unique_ptr<imp> m_ptr;
+public:
+    rewrite_rule_set(ro_environment const & env);
+    rewrite_rule_set(rewrite_rule_set const & rs);
+    ~rewrite_rule_set();
+    /**
+       \brief Convert the theorem \c th with proof \c proof into conditional rewrite rules, and
+       insert the rules into this rule set. The new rules are tagged with the given \c id.
+    */
+    void insert(name const & id, expr const & th, expr const & proof);
+    /**
+       \brief Convert the theorem/axiom named \c th_name in the environment into conditional rewrite rules,
+       and insert the rules into this rule set. The new rules are tagged with the theorem name.
+
+       This method throws an exception if the environment does not have a theorem/axiom named \c th_name.
+    */
+    void insert(name const & th_name);
+
+    /**
+       \brief Enable/disable the conditional rewrite rules tagged with the given identifier.
+    */
+    void enable(name const & id, bool flag);
+    /**
+       \brief Return true iff the conditional rewrite rules tagged with the given id are enabled.
+    */
+    bool enabled(name const & id) const;
+
+    typedef std::function<bool(expr const &, expr const &, bool is_permutation, expr const &)> match_fn;
+    typedef std::function<void(name const &, expr const &, expr const &, bool)> visit_fn;
+
+    /**
+       \brief Execute <tt>fn(lhs, ceq, is_perm, proof)</tt> for each (enabled) rule whose the left-hand-side may
+       match \c e.
+       The traversal is interrupted as soon as \c fn returns true.
+
+       The redundant argument \c lhs is the left-hand-side of \c ceq.
+       The redundant argument \c is_perm is true iff \c ceq is a permutation rule.
+
+       The argument \c proof is the proof for \c ceq.
+    */
+    void for_each_match_candidate(expr const & e, match_fn const & fn);
+
+    /**
+       \brief Execute <tt>fn(id, ceq, proof, enabled)</tt> for each rule in this rule set.
+    */
+    void for_each(visit_fn const & fn);
+
+    /**
+       \brief Pretty print this rule set.
+    */
+    format pp(formatter const & fmt, options const & opts) const;
+};
+}