Composite function in C++ -

i beginner in c++ , want simple example of composite function. example, in matlab, can write

a = @(x) 2*x b = @(y) 3*y a(b(1)) 

answer 6

i searched following questions. function composition in c++ / c++11 , function composition in c++

but created using advanced features, such templates, not familiar @ time. there simple , more direct way achieve this? in above matlab code, user not need know implementation of function handles. user can use proper syntax result. there such way in c++?

** edit:**

in above code, putting value @ end. however, if want pass result third function, matlab can still consider function. but, how in c++?

for example, in addition above code, consider code:

c = @(p,q) a(p)* b(q)  %this results function c(1,2) answer=12  d = @(r) a(b(r)) d(1) answer=6  function [ output1 ] = f1( arg1 ) val = 2.0; output1 = feval(arg1,val) end  f1(d) answer = 12 

in code, c takes 2 functions input , d composite function. in next example, function f1 takes function argument , use matlab builtin function feval evaluate function @ val.

how can achieve in c++?

how about:

#include <iostream>  int main(int, char**) {     auto = [](int x) { return 2 * x; };     auto b = [](int y) { return 3 * y; };      (int = 0; < 5; ++i)         std::cout << << " -> " << a(b(i)) << std::endl;      return 0; }