Index: src/Common/ScopedMap.h
===================================================================
--- src/Common/ScopedMap.h	(revision e491159c00c09ae82c7b254c1c76fba21a6d2d5c)
+++ src/Common/ScopedMap.h	(revision e491159c00c09ae82c7b254c1c76fba21a6d2d5c)
@@ -0,0 +1,290 @@
+//
+// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
+//
+// The contents of this file are covered under the licence agreement in the
+// file "LICENCE" distributed with Cforall.
+//
+// ScopedMap.h --
+//
+// Author           : Aaron B. Moss
+// Created On       : Wed Dec 2 11:37:00 2015
+// Last Modified By : Aaron B. Moss
+// Last Modified On : Wed Dec 2 11:37:00 2015
+// Update Count     : 1
+//
+
+#ifndef _SCOPEDMAP_H
+#define _SCOPEDMAP_H
+
+#include <cassert>
+#include <iterator>
+#include <map>
+#include <utility>
+#include <vector>
+
+/// A map where the items are placed into nested scopes;
+/// inserted items are placed into the innermost scope, lookup looks from the innermost scope outward
+template<typename Key, typename Value>
+class ScopedMap {
+	typedef std::map< Key, Value > Scope;
+	typedef std::vector< Scope > ScopeList;
+
+	ScopeList scopes; ///< scoped list of maps
+public:
+	typedef typename Scope::key_type key_type;
+	typedef typename Scope::mapped_type mapped_type;
+	typedef typename Scope::value_type value_type;
+	typedef typename ScopeList::size_type size_type;
+	typedef typename ScopeList::difference_type difference_type;
+	typedef typename Scope::reference reference;
+	typedef typename Scope::const_reference const_reference;
+	typedef typename Scope::pointer pointer;
+	typedef typename Scope::const_pointer const_pointer;
+
+	class iterator : public std::iterator< std::bidirectional_iterator_tag,
+	                                       value_type > {
+	friend class ScopedMap;
+	friend class const_iterator;
+		typedef typename std::map< Key, Value >::iterator wrapped_iterator;
+		typedef typename std::vector< std::map< Key, Value > > scope_list;
+		typedef typename scope_list::size_type size_type;
+
+		/// Checks if this iterator points to a valid item
+		bool is_valid() const {
+			return it != (*scopes)[i].end();
+		}
+
+		/// Increments on invalid
+		iterator& next_valid() {
+			if ( ! is_valid() ) { ++(*this); }
+			return *this;
+		}
+
+		/// Decrements on invalid
+		iterator& prev_valid() {
+			if ( ! is_valid() ) { --(*this); }
+			return *this;
+		}
+
+		iterator(scope_list &_scopes, const wrapped_iterator &_it, size_type _i)
+			: scopes(&_scopes), it(_it), i(_i) {}
+	public:
+		iterator(const iterator &that) : scopes(that.scopes), it(that.it), i(that.i) {}
+		iterator& operator= (const iterator &that) {
+			scopes = that.scopes; i = that.i; it = that.it;
+			return *this;
+		}
+
+		reference operator* () { return *it; }
+		pointer operator-> () { return it.operator->(); }
+
+		iterator& operator++ () {
+			if ( it == (*scopes)[i].end() ) {
+				if ( i == 0 ) return *this;
+				--i;
+				it = (*scopes)[i].begin();
+			} else {
+				++it;
+			}
+			return next_valid();
+		}
+		iterator operator++ (int) { iterator tmp = *this; ++(*this); return tmp; }
+
+		iterator& operator-- () {
+			// may fail if this is the begin iterator; allowed by STL spec
+			if ( it == (*scopes)[i].begin() ) {
+				++i;
+				it = (*scopes)[i].end();
+			}
+			--it;
+			return prev_valid();
+		}
+		iterator operator-- (int) { iterator tmp = *this; --(*this); return tmp; }
+
+		bool operator== (const iterator &that) {
+			return scopes == that.scopes && i == that.i && it == that.it;
+		}
+		bool operator!= (const iterator &that) { return !( *this == that ); }
+
+	private:
+		scope_list *scopes;
+		wrapped_iterator it;
+		size_type i;
+	};
+
+	class const_iterator : public std::iterator< std::bidirectional_iterator_tag,
+	                                             value_type > {
+	friend class ScopedMap;
+		typedef typename std::map< Key, Value >::iterator wrapped_iterator;
+		typedef typename std::map< Key, Value >::const_iterator wrapped_const_iterator;
+		typedef typename std::vector< std::map< Key, Value > > scope_list;
+		typedef typename scope_list::size_type size_type;
+
+		/// Checks if this iterator points to a valid item
+		bool is_valid() const {
+			return it != (*scopes)[i].end();
+		}
+
+		/// Increments on invalid
+		const_iterator& next_valid() {
+			if ( ! is_valid() ) { ++(*this); }
+			return *this;
+		}
+
+		/// Decrements on invalid
+		const_iterator& prev_valid() {
+			if ( ! is_valid() ) { --(*this); }
+			return *this;
+		}
+
+		const_iterator(scope_list const &_scopes, const wrapped_const_iterator &_it, size_type _i)
+			: scopes(&_scopes), it(_it), i(_i) {}
+	public:
+		const_iterator(const iterator &that) : scopes(that.scopes), it(that.it), i(that.i) {}
+		const_iterator(const const_iterator &that) : scopes(that.scopes), it(that.it), i(that.i) {}
+		const_iterator& operator= (const iterator &that) {
+			scopes = that.scopes; i = that.i; it = that.it;
+			return *this;
+		}
+		const_iterator& operator= (const const_iterator &that) {
+			scopes = that.scopes; i = that.i; it = that.it;
+			return *this;
+		}
+
+		const_reference operator* () { return *it; }
+		const_pointer operator-> () { return it.operator->(); }
+
+		const_iterator& operator++ () {
+			if ( it == (*scopes)[i].end() ) {
+				if ( i == 0 ) return *this;
+				--i;
+				it = (*scopes)[i].begin();
+			} else {
+				++it;
+			}
+			return next_valid();
+		}
+		const_iterator operator++ (int) { const_iterator tmp = *this; ++(*this); return tmp; }
+
+		const_iterator& operator-- () {
+			// may fail if this is the begin iterator; allowed by STL spec
+			if ( it == (*scopes)[i].begin() ) {
+				++i;
+				it = (*scopes)[i].end();
+			}
+			--it;
+			return prev_valid();
+		}
+		const_iterator operator-- (int) { const_iterator tmp = *this; --(*this); return tmp; }
+
+		bool operator== (const const_iterator &that) {
+			return scopes == that.scopes && i == that.i && it == that.it;
+		}
+		bool operator!= (const const_iterator &that) { return !( *this == that ); }
+
+	private:
+		scope_list const *scopes;
+		wrapped_const_iterator it;
+		size_type i;
+	};
+
+	/// Starts a new scope
+	void beginScope() {
+		scopes.emplace_back();
+	}
+
+	/// Ends a scope; invalidates any iterators pointing to elements of that scope
+	void endScope() {
+		scopes.pop_back();
+		assert( ! scopes.empty() );
+	}
+
+	/// Default constructor initializes with one scope
+	ScopedMap() { beginScope(); }
+
+	iterator begin() { return iterator(scopes, scopes.back().begin(), scopes.size()-1).next_valid(); }
+	const_iterator begin() const { return const_iterator(scopes, scopes.back().begin(), scopes.size()-1).next_valid(); }
+	const_iterator cbegin() const { return const_iterator(scopes, scopes.back().begin(), scopes.size()-1).next_valid(); }
+	iterator end() { return iterator(scopes, scopes[0].end(), 0); }
+	const_iterator end() const { return const_iterator(scopes, scopes[0].end(), 0); }
+	const_iterator cend() const { return const_iterator(scopes, scopes[0].end(), 0); }
+
+	/// Gets the index of the current scope (counted from 1)
+	size_type currentScope() const { return scopes.size(); }
+
+	/// Finds the given key in the outermost scope it occurs; returns end() for none such
+	iterator find( const Key &key ) {
+		for ( size_type i = scopes.size() - 1; ; --i ) {
+			typename Scope::iterator val = scopes[i].find( key );
+			if ( val != scopes[i].end() ) return iterator( scopes, val, i );
+			if ( i == 0 ) break;
+		}
+		return end();
+	}
+	const_iterator find( const Key &key ) const {
+			return const_iterator( const_cast< ScopedMap< Key, Value >* >(this)->find( key ) );
+	}
+
+	/// Finds the given key in the outermost scope inside the given scope where it occurs
+	iterator findNext( const_iterator &it, const Key &key ) {
+		if ( it.i == 0 ) return end();
+		for ( size_type i = it.i - 1; ; --i ) {
+			typename Scope::iterator val = scopes[i].find( key );
+			if ( val != scopes[i].end() ) return iterator( scopes, val, i );
+			if ( i == 0 ) break;
+		}
+		return end();
+	}
+	const_iterator findNext( const_iterator &it, const Key &key ) const {
+			return const_iterator( const_cast< ScopedMap< Key, Value >* >(this)->findNext( it, key ) );
+	}
+
+	/// Inserts the given key-value pair into the outermost scope
+	std::pair< iterator, bool > insert( const value_type &value ) {
+		std::pair< typename Scope::iterator, bool > res = scopes.back().insert( value );
+		return std::make_pair( iterator(scopes, res.first, scopes.size()-1), res.second );
+	}
+
+	std::pair< iterator, bool > insert( value_type &&value ) {
+		std::pair< typename Scope::iterator, bool > res = scopes.back().insert( std::move( value ) );
+		return std::make_pair( iterator(scopes, std::move( res.first ), scopes.size()-1), std::move( res.second ) );
+	}
+
+	std::pair< iterator, bool > insert( const Key &key, const Value &value ) { return insert( std::make_pair( key, value ) ); }
+	std::pair< iterator, bool > insert( const Key &key, Value &&value ) { return insert( std::make_pair( key, std::move( value ) ) ); }
+
+	Value& operator[] ( const Key &key ) {
+		iterator slot = find( key );
+		if ( slot != end() ) return slot->second;
+		return insert( key, Value() ).first->second;
+	}
+
+	iterator erase( iterator pos ) {
+		Scope& scope = (*pos.scopes) [ pos.i ];
+		const typename iterator::wrapped_iterator& new_it = scope.erase( pos.it );
+		iterator it( *pos.scopes, new_it, pos.i );
+		return it.next_valid();
+	}
+
+	size_type count( const Key &key ) const {
+		size_type c = 0;
+		auto it = find( key );
+		auto end = cend();
+
+		while(it != end) {
+			c++;
+			it = findNext(it, key);
+		}
+
+		return c;
+	}
+
+};
+
+#endif // _SCOPEDMAP_H
+
+// Local Variables: //
+// tab-width: 4 //
+// mode: c++ //
+// compile-command: "make install" //
+// End: //
Index: src/Common/utility.h
===================================================================
--- src/Common/utility.h	(revision 79970ed6c19a6660b1238fe9021a3df4e5884245)
+++ src/Common/utility.h	(revision e491159c00c09ae82c7b254c1c76fba21a6d2d5c)
@@ -17,10 +17,11 @@
 #define _UTILITY_H
 
+#include <cctype>
 #include <iostream>
+#include <iterator>
+#include <list>
+#include <memory>
 #include <sstream>
-#include <iterator>
 #include <string>
-#include <cctype>
-#include <list>
 
 template< typename T >
@@ -246,4 +247,19 @@
 }
 
+template< typename ThisType >
+class RefCountSingleton {
+  public:
+	static std::shared_ptr<ThisType> get() {
+		if( global_instance.expired() ) {
+			std::shared_ptr<ThisType> new_instance = std::make_shared<ThisType>();
+			global_instance = new_instance;
+			return std::move(new_instance);
+		}
+		return global_instance.lock();
+	}
+  private:
+	static std::weak_ptr<ThisType> global_instance;
+};
+
 #endif // _UTILITY_H