Question

Need prettier solution of below example but with std::accumulate.

#include <algorithm> #include <vector> #include <iostream>  class Object { public:     Object( double a, double b ):         a_( a ),         b_( b )     {}      double GetA() const { return a_; }     double GetB() const { return b_; }     // other methods private:     double a_;     double b_; };  class Calculator { public:     Calculator( double& result ):         result_( result )     {}      void operator() ( const Object& object )     {         // some formula         result_ += object.GetA() * object.GetB();     } private:     double& result_; };  int main() {     std::vector< Object > collection;     collection.push_back( Object( 1, 2 ) );     collection.push_back( Object( 3, 4 ) );      double result = 0.0;     std::for_each( collection.begin(), collection.end(),                    Calculator( result ) );      std::cout << 'result = ' << result << std::endl;      return 0; } 

Answer 1

do changes in Calculator and main function.

struct Calculator {     double operator() ( double result, const Object& obj )     {         return result + ( obj.GetA() * obj.GetB());     }  };  int main() {     std::vector< Object > collection;     collection.push_back( Object( 1, 2 ) );     collection.push_back( Object( 3, 4 ) );      double result = std::accumulate( collection.begin(), collection.end(), 0, Calculator() );     std::cout << 'result = ' << result << std::endl;      return 0; } 

also it could be better:

double sumABProduct( double result, const Object& obj ) {     return result + ( obj.GetA() * obj.GetB()); }  double result = std::accumulate( collection.begin(), collection.end(), 0, sumABProduct );