initial import

example/parser.cpp

@@ -0,0 +1,109 @@
+
+//          Copyright Oliver Kowalke 2014.
+// 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 <cstdio>
+#include <functional>
+#include <iostream>
+#include <sstream>
+#include <thread>
+
+#include <boost/coroutine2/all.hpp>
+
+/*
+ * grammar:
+ *   P ---> E '\0'
+ *   E ---> T {('+'|'-') T}
+ *   T ---> S {('*'|'/') S}
+ *   S ---> digit | '(' E ')'
+ */
+class Parser{
+   char next;
+   std::istream& is;
+   std::function<void(char)> cb;
+
+   char pull(){
+        return std::char_traits<char>::to_char_type(is.get());
+   }
+
+   void scan(){
+       do{
+           next=pull();
+       }
+       while(isspace(next));
+   }
+
+public:
+   Parser(std::istream& is_,std::function<void(char)> cb_) :
+      next(), is(is_), cb(cb_)
+    {}
+
+   void run() {
+      scan();
+      E();
+   }
+
+private:
+   void E(){
+      T();
+      while (next=='+'||next=='-'){
+         cb(next); 
+         scan();
+         T();
+      }
+   }
+
+   void T(){
+      S();
+      while (next=='*'||next=='/'){
+         cb(next); 
+         scan();
+         S();
+      }
+   }
+
+   void S(){
+      if (std::isdigit(next)){
+         cb(next);
+         scan();
+      }
+      else if(next=='('){
+         cb(next); 
+         scan();
+         E();
+         if (next==')'){
+             cb(next); 
+             scan();
+         }else{
+             exit(2);
+         }
+      }
+      else{
+         exit(3);
+      }
+   }
+};
+
+typedef boost::coroutines2::asymmetric_coroutine< char > coro_t;
+
+int main() {
+    std::istringstream is("1+1");
+    // invert control flow
+    coro_t::pull_type seq(
+            boost::coroutines2::fixedsize_stack(),
+            [&is]( coro_t::push_type & yield) {
+                Parser p( is,
+                          [&yield](char ch){
+                            yield(ch);
+                          });
+                p.run();
+            });
+
+    // user-code pulls parsed data from parser
+    for(char c:seq){
+        printf("Parsed: %c\n",c);
+    }
+}
+