C++ Reactive Programming

The Scan Operator

The scan Operator applies a function on each element of a Stream sequentially and accumulates the value into a seed value. The following program produces average of a series of numbers as and when the values are accumulated:

//----------- Scan.cpp 
#include "rxcpp/rx.hpp" 
#include "rxcpp/rx-test.hpp" 
#include <ioStream> 
int main() { 
    int count = 0; 
    auto values = rxcpp::observable<>::range(1, 20). 
        scan( 0,[&count](int seed, int v){ 
                count++; 
                return seed + v; 
            }); 
    values.subscribe( 
        [&](int v){printf("Average through Scan: %fn", (double)v/count);}, 
        [](){printf("OnCompletedn");}); 
} 

The running average will be printed on to the console. OnNext functor will be called twenty times before OnCompleted is called.