How std::transform and std::plus work together?

<p>I was reading C++ reference and came across std::plus function with an example. Which is pretty straight forward, its simply adds lhs and rhs. The code was:</p><pre><br /><code>#include <functional><br />#include <iostream><br /><br />int main()<br />{<br /> std::string a = "Hello ";<br /> const char* b = "world";<br /> std::cout << std::plus<>{}(a, b) << '\n';<br />}<br /></code><br /></pre><p>output: Hello world</p><p>I changed it to</p><pre><br /><code>#include <functional><br />#include <iostream><br /><br />int main()<br />{<br /> int a = 5;<br /> int b = 1;<br /> std::cout << std::plus<int>{}(a, b) << '\n';<br />}<br /></code><br /></pre><p>output : 6</p><p>Now I made</p><pre><br /><code>foo vector = 10 20 30 40 50<br />bar vector = 11 21 31 41 51<br /></code><br /></pre><p>I called:</p><pre><br /><code>std::transform (foo.begin(), foo.end(), bar.begin(), foo.begin(), std::plus<int>());<br /></code><br /></pre><p>and it gave 21 41 61 81 101 which I understand it is adding up both foo and bar. But how it was passed to std::plus function?</p><br /><h2>Click here view more answers <a href="http://ift.tt/20RXA31">http://ift.tt/20RXA31</a></h2>