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extern/stdcxx/4.2.1/examples/manual/memfunc.cpp

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+/**************************************************************************
+ *
+ * memfunc.cpp - Example program for mem_fun and other member function
+ *               pointer wrappers.
+ *
+ * $Id: memfunc.cpp 550991 2007-06-26 23:58:07Z sebor $
+ *
+ ***************************************************************************
+ *
+ * Licensed to the Apache Software  Foundation (ASF) under one or more
+ * contributor  license agreements.  See  the NOTICE  file distributed
+ * with  this  work  for  additional information  regarding  copyright
+ * ownership.   The ASF  licenses this  file to  you under  the Apache
+ * License, Version  2.0 (the  "License"); you may  not use  this file
+ * except in  compliance with the License.   You may obtain  a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the  License is distributed on an  "AS IS" BASIS,
+ * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY  KIND, either  express or
+ * implied.   See  the License  for  the  specific language  governing
+ * permissions and limitations under the License.
+ *
+ * Copyright 1994-2006 Rogue Wave Software.
+ * 
+ **************************************************************************/
+
+#if defined (__IBMCPP__)
+#  include <rw/_config.h>
+   // disable implicit inclusion to work around 
+   // a limitation in IBM VisualAge 5 (PR #26959) 
+#  ifndef _RWSTD_NO_IMPLICIT_INCLUSION
+#    define _RWSTD_NO_IMPLICIT_INCLUSION 
+#  endif   // _RWSTD_NO_IMPLICIT_INCLUSION
+#endif   // __IBMCPP__
+
+#include <algorithm>   // for for_each, stable_sort
+#include <cstddef>     // for size_t
+#include <functional>  // for greater
+#include <iomanip>     // for setprecision, setw
+#include <ios>         // for fixed, left, right
+#include <iostream>    // for cout
+#include <vector>      // for vector
+
+#include <examples.h>
+
+
+// Very large city class
+class Megapolis
+{
+public:
+
+    Megapolis (const char *s = "", double n = 0)
+        :population(n), cityName(s) { }
+
+    // The following function cannot return void due to limitations in 
+    // some current C++ implementations. 
+    virtual std::size_t byPopulation () const {
+        std::cout << std::setw (12) << std::left << cityName
+                  << std::setw (12) << std::left << "Megapolis"
+                  << std::setw (5) << std::right
+                  << std::fixed << std::setprecision (1)
+                  << population << '\n';
+        return 0;
+    }
+
+    bool operator< ( const Megapolis* ptr_ ) {
+        return population > ptr_->population;
+    }
+
+    double population;
+
+protected:
+
+    const char* cityName;
+};
+
+
+// City and surrounding area class
+struct Metropolis: public Megapolis
+{
+    Metropolis (const char *s = "", double n = 0)
+        : Megapolis (s, n){ }
+
+    virtual std::size_t byPopulation () const {
+        std::cout << std::setw (12) << std::left <<  cityName
+                  << std::setw (12) << std::left << "Metropolis"
+                  << std::setw (5) << std::right
+                  << std::fixed << std::setprecision (1)
+                  << population << '\n';
+        return 0;
+    }
+};
+
+
+namespace std {
+
+// specialize the standard function object for Megapolis*
+template<>
+struct greater<Megapolis*>
+{
+    typedef const Megapolis* first_argument_type;
+    typedef const Megapolis* second_argument_type;
+    typedef bool             result_type;
+
+    result_type
+    operator() (first_argument_type x, second_argument_type y) const {
+        return y->population < x->population;
+    }
+};
+
+}   // namespace std
+
+
+int main ()
+{
+    // Create a vector of very large cities
+    std::vector<Megapolis*, std::allocator<Megapolis*> > cities;
+
+    cities.push_back (new Megapolis ("Calcutta", 12));
+    cities.push_back (new Megapolis ("Tokyo", 26.8));
+    cities.push_back (new Megapolis ("Delhi", 10)); 
+    cities.push_back (new Megapolis ("Bombay", 15));
+  
+    cities.push_back (new Metropolis ("Cairo", 12));
+    cities.push_back (new Metropolis ("New York", 7.5));
+    cities.push_back (new Metropolis ("Los Angeles", 3.7)); 
+    cities.push_back (new Metropolis ("Jakarta", 8.2));
+  
+    // Now use mem_fun to pass byPopulation member function
+    // of Megapolis to the for_each function.
+    std::cout << "City        Type        Population (millions)\n";
+    std::cout << "----------- ----------- ---------------------\n";
+
+    std::for_each (cities.begin(), cities.end(),
+                   std::mem_fun (&Megapolis::byPopulation));
+
+    std::cout << "\nAfter sorting...\n\n";
+
+    // Sort
+    std::stable_sort (cities.begin (), cities.end (),
+                      std::greater<Megapolis*>());
+
+    std::for_each (cities.begin (), cities.end (),
+                   std::mem_fun (&Megapolis::byPopulation));
+
+    // Free allocated memory
+    while (!cities.empty ()) {
+        delete cities.back ();
+        cities.pop_back ();
+    }
+
+    return 0;
+}