coroutine: update of interface

[SVN r85105]

example/cpp11/layout.cpp

@@ -0,0 +1,50 @@
+
+//          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/coroutine/all.hpp>
+
+struct FinalEOL{
+    ~FinalEOL(){
+        std::cout << std::endl;
+    }
+};
+
+int main(int argc,char* argv[]){
+    std::vector<std::string> words{
+        "peas", "porridge", "hot", "peas",
+        "porridge", "cold", "peas", "porridge",
+        "in", "the", "pot", "nine",
+        "days", "old" };
+
+    int num=5,width=15;
+    boost::coroutines::coroutine<std::string>::push_type writer(
+        [&](boost::coroutines::coroutine<std::string>::pull_type& in){
+            // 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;
+            }
+        });
+
+    std::copy(std::begin(words),std::end(words),std::begin(writer));
+
+    return 0;
+}