Adding upstream version 14.2.21.upstream/14.2.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 58 insertions, 0 deletions

diff --git a/src/boost/libs/flyweight/example/fibonacci.cpp b/src/boost/libs/flyweight/example/fibonacci.cpp
new file mode 100644
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+++ b/src/boost/libs/flyweight/example/fibonacci.cpp
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+/* Boost.Flyweight example of flyweight-based memoization.
+ *
+ * Copyright 2006-2008 Joaquin M Lopez Munoz.
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See http://www.boost.org/libs/flyweight for library home page.
+ */
+
+#include <boost/flyweight.hpp>
+#include <boost/flyweight/key_value.hpp>
+#include <boost/flyweight/no_tracking.hpp>
+#include <boost/noncopyable.hpp>
+#include <iostream>
+
+using namespace boost::flyweights;
+
+/* Memoized calculation of Fibonacci numbers */
+
+/* This class takes an int n and calculates F(n) at construction time */
+
+struct compute_fibonacci;
+
+/* A Fibonacci number can be modeled as a key-value flyweight
+ * We choose the no_tracking policy so that the calculations
+ * persist for future use throughout the program. See
+ * Tutorial: Configuring Boost.Flyweight: Tracking policies for
+ * further information on tracking policies.
+ */
+
+typedef flyweight<key_value<int,compute_fibonacci>,no_tracking> fibonacci;
+
+/* Implementation of compute_fibonacci. Note that the construction
+ * of compute_fibonacci(n) uses fibonacci(n-1) and fibonacci(n-2),
+ * which effectively memoizes the computation.
+ */
+
+struct compute_fibonacci:private boost::noncopyable
+{
+  compute_fibonacci(int n):
+    result(n==0?0:n==1?1:fibonacci(n-2).get()+fibonacci(n-1).get())
+  {}
+
+  operator int()const{return result;}
+  int result;
+};
+
+int main()
+{
+  /* list some Fibonacci numbers */
+
+  for(int n=0;n<40;++n){
+    std::cout<<"F("<<n<<")="<<fibonacci(n)<<std::endl;
+  }
+
+  return 0;
+}