CPP/C++0x/Lambda

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Lambda.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <utility>
 
void Lambda();
 
void Equivalent();
 
int main()
{
 
}
 
 
void Lambda()
{
    std::vector<std::pair<int, float> > v{
         {1, 4.5}, {3, 6.7}, {9, 7.8}
    };
 
    auto it=std::find_if(v.begin(), v.end(), [](std::pair<int, float> p) {
        return p.first==3;
    }); // This lambda expression (or "anonymous function") lets you "on the fly" define a function to be used.
    // Here, we are comparing the .first of all of the items in the container to "3"
    std::cout << it->second;
}
 
struct Equals
{
  Equals(const int value)
  {
    CompareValue = value;
  }
 
  bool operator()(const std::pair<int, float>& value)
  {
    return value.first == 3;
  }
 
  int CompareValue;
};
 
void Equivalent()
{
    std::vector<std::pair<int, float> > v{
         {1, 4.5}, {3, 6.7}, {9, 7.8}
    };
 
    // This works, but this following is shorter:
//     Equals myEquals;
//     myEquals.CompareValue = 3;
//     auto it=std::find_if(v.begin(), v.end(), myEquals);
 
    auto it=std::find_if(v.begin(), v.end(), Equals(3));
 
    std::cout << it->second;
}

CMakeLists.txt

cmake_minimum_required(VERSION 2.6)
 
Project(Lambda)
ADD_EXECUTABLE(Lambda Lambda.cpp)