coroutine: update of interface

[SVN r85105]

example/cpp03/layout.cpp

@@ -0,0 +1,71 @@
+
+//          Copyright Nat Goodspeed 2013.
+// 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)
+
+#include <iostream>
+#include <iomanip>
+#include <vector>
+#include <string>
+#include <utility>
+
+#include <boost/assign/list_of.hpp>
+#include <boost/bind.hpp>
+#include <boost/coroutine/all.hpp>
+#include <boost/range.hpp>
+
+struct FinalEOL
+{
+    ~FinalEOL() { std::cout << std::endl; }
+};
+
+void layout(boost::coroutines::coroutine<std::string>::pull_type& in, int num, int width)
+{
+    // Finish the last line when we leave by whatever means
+    FinalEOL eol;
+
+    // Pull values from upstream, lay them out 'num' to a line
+    for (;;)
+    {
+        for (int i = 0; i < num; ++i)
+        {
+            // when we exhaust the input, stop
+            if (! in)
+                return;
+
+            std::cout << std::setw(width) << in.get();
+            // now that we've handled this item, advance to next
+            in();
+        }
+        // after 'num' items, line break
+        std::cout << std::endl;
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    std::vector<std::string> words = boost::assign::list_of
+        ("peas")
+        ("porridge")
+        ("hot")
+        ("peas")
+        ("porridge")
+        ("cold")
+        ("peas")
+        ("porridge")
+        ("in")
+        ("the")
+        ("pot")
+        ("nine")
+        ("days")
+        ("old")
+    ;
+
+    boost::coroutines::coroutine<std::string>::push_type writer(
+        boost::bind(layout, _1, 5, 15));
+
+    std::copy(boost::begin(words), boost::end(words), boost::begin(writer));
+
+    return 0;
+}