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

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+/**************************************************************************
+ *
+ * funct_ob.cpp - Example program for function objects.
+ *
+ * $Id: funct_ob.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.
+ * 
+ **************************************************************************/
+
+#include <algorithm>
+#include <deque>
+#include <functional>
+#include <iostream>
+#include <iterator>
+#include <vector>
+
+
+// Create a new function object from unary_function.
+template <class Arg, class Result>
+struct factorial: public std::unary_function<Arg, Result>
+{
+    Result operator() (const Arg &arg) {
+        Result a = 1;
+        for (Arg i = 2; i <= arg; i++)
+            a *= i;
+        return a;
+    }
+};
+
+
+int main ()
+{
+    // Typedefs for convenience.
+    typedef std::deque<int, std::allocator<int> >    Deque;
+    typedef std::vector<long, std::allocator<long> > Vector;
+
+    // Initialize a deque with an array of integers.
+    Deque::value_type arr[] = { 1, 2, 3, 4, 5, 6, 7 };
+    Deque d (arr, arr + sizeof arr / sizeof *arr);
+
+    // Create an empty vector to store the factorials.
+    Vector v;
+
+    // Transform the numbers in the deque to their factorials
+    // and store in the vector.
+    std::transform (d.begin (), d.end (), 
+                    std::back_inserter (v),
+                    factorial<Deque::value_type, Vector::value_type>());
+
+    // Create an iterator to output deque elements.
+    std::ostream_iterator<Deque::value_type, 
+                          char, 
+                          std::char_traits<char> > outd (std::cout, " ");
+
+    // Print the results.
+    std::cout << "The following numbers: \n     ";
+    std::copy (d.begin (), d.end (), outd);
+
+    // Create an iterator to output vector elements.
+    std::ostream_iterator<Vector::value_type, 
+                          char, 
+                          std::char_traits<char> > outv (std::cout, " ");
+
+    std::cout << std::endl;
+    std::cout << "\nHave the factorials: \n     ";
+    std::copy (v.begin (), v.end (), outv);
+    std::cout << std::endl;
+
+    return 0;
+}