ceph/src/boost/libs/poly_collection/example/basic_function.cpp

   1 /* Copyright 2016-2017 Joaquin M Lopez Munoz.
   2  * Distributed under the Boost Software License, Version 1.0.
   3  * (See accompanying file LICENSE_1_0.txt or copy at
   4  * http://www.boost.org/LICENSE_1_0.txt)
   5  *
   6  * See http://www.boost.org/libs/poly_collection for library home page.
   7  */
   8
   9 /* basic usage of boost::function_collection */
  10
  11 #include <boost/poly_collection/function_collection.hpp>
  12 #include <functional>
  13 #include <memory>
  14 #include <random>
  15 #include <vector>
  16 #include "rolegame.hpp"
  17
  18 int main()
  19 {
  20 //[basic_function_1
  21   std::vector<std::unique_ptr<sprite>> sprs;
  22   std::vector<std::string>             msgs;
  23   std::vector<window>                  wnds;
  24 //]
  25
  26   // populate sprs
  27   std::mt19937                 gen{92748}; // some arbitrary random seed
  28   std::discrete_distribution<> rnd{{1,1,1}};
  29   for(int i=0;i<4;++i){        // assign each type with 1/3 probability
  30     switch(rnd(gen)){
  31       case 0: sprs.push_back(std::make_unique<warrior>(i));;break;
  32       case 1: sprs.push_back(std::make_unique<juggernaut>(i));break;
  33       case 2: sprs.push_back(std::make_unique<goblin>(i));break;
  34     }
  35   }
  36
  37   // populate msgs
  38   msgs.push_back("\"stamina: 10,000\"");
  39   msgs.push_back("\"game over\"");
  40
  41   // populate wnds
  42   wnds.emplace_back("pop-up 1");
  43   wnds.emplace_back("pop-up 2");
  44
  45 //[basic_function_2
  46 //=  #include <boost/poly_collection/function_collection.hpp>
  47 //=  ...
  48 //=
  49   // function signature accepting std::ostream& and returning nothing
  50   using render_callback=void(std::ostream&);
  51
  52   boost::function_collection<render_callback> c;
  53 //]
  54
  55 //[basic_function_3
  56 //<-
  57   auto render_sprite=[](const sprite& s){
  58 //->
  59 //=  auto render_sprite(const sprite& s){
  60     return [&](std::ostream& os){s.render(os);};
  61   }/*<-*/;/*->*/
  62
  63 //<-
  64   auto render_message=[](const std::string& m){
  65 //->
  66 //=  auto render_message(const std::string& m){
  67     return [&](std::ostream& os){os<<m;};
  68   }/*<-*/;/*->*/
  69
  70 //<-
  71   auto render_window=[](const window& w){
  72 //->
  73 //=  auto render_window(const window& w){
  74     return [&](std::ostream& os){w.display(os);};
  75   }/*<-*/;/*->*/
  76 //=  ...
  77 //=
  78   for(const auto& ps:sprs)c.insert(render_sprite(*ps));
  79   for(const auto& m:msgs)c.insert(render_message(m));
  80   for(const auto& w:wnds)c.insert(render_window(w));
  81 //]
  82
  83 //[basic_function_4
  84   const char* comma="";
  85   for(const auto& cbk:c){
  86     std::cout<<comma;
  87     cbk(std::cout);
  88     comma=",";
  89   }
  90   std::cout<<"\n";
  91 //]
  92
  93 //[basic_function_5
  94   auto cbk=*c.begin();
  95   cbk(std::cout); // renders first element to std::cout
  96   std::function<render_callback> f=cbk;
  97   f(std::cout);   // exactly the same
  98 //]
  99
 100 //[basic_function_6
 101 //=  *c.begin()=render_message("last minute message"); // compile-time error
 102 //]
 103 }