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+// file : cutl/container/key.hxx
+// copyright : Copyright (c) 2009-2012 Code Synthesis Tools CC
+// license : MIT; see accompkeying LICENSE file
+
+#ifndef CUTL_CONTAINER_KEY_HXX
+#define CUTL_CONTAINER_KEY_HXX
+
+namespace cutl
+{
+ namespace container
+ {
+ // A modifiable map key wrapper that can be used to implement multi-
+ // index containers, as discussed in the following post:
+ //
+ // http://www.codesynthesis.com/~boris/blog/2012/09/11/emulating-boost-multi-index-with-std-containers/
+ //
+ template <class T1, class T2 = void, class T3 = void>
+ struct key;
+
+ template <class T1>
+ struct key<T1, void, void>
+ {
+ mutable const T1* p1;
+
+ key (): p1 (0) {}
+ key (const T1& r1): p1 (&r1) {}
+ void assign (const T1& r1) const {p1 = &r1;}
+
+ bool operator< (const key& x) const {return *p1 < *x.p1;}
+ };
+
+ template <class T1, class T2>
+ struct key<T1, T2, void>
+ {
+ mutable const T1* p1;
+ mutable const T2* p2;
+
+ key (): p1 (0), p2 (0) {}
+ key (const T1& r1, const T2& r2): p1 (&r1), p2 (&r2) {}
+ void assign (const T1& r1, const T2& r2) const {p1 = &r1; p2 = &r2;}
+
+ bool operator< (const key& x) const
+ {
+ return *p1 < *x.p1 || (!(*x.p1 < *p1) && *p2 < *x.p2);
+ }
+ };
+
+ template <class T1, class T2, class T3>
+ struct key
+ {
+ mutable const T1* p1;
+ mutable const T2* p2;
+ mutable const T3* p3;
+
+ key (): p1 (0), p2 (0), p3 (0) {}
+ key (const T1& r1, const T2& r2, const T3& r3)
+ : p1 (&r1), p2 (&r2) , p3 (&r3) {}
+ void assign (const T1& r1, const T2& r2, const T3& r3) const
+ {p1 = &r1; p2 = &r2; p3 = &r3;}
+
+ bool operator< (const key& x) const
+ {
+ return (*p1 < *x.p1 ||
+ (!(*x.p1 < *p1) && (*p2 < *x.p2 ||
+ (!(*x.p2 < *p2) && *p3 < *x.p3))));
+ }
+ };
+ }
+}
+
+#endif // CUTL_CONTAINER_KEY_HXX