flow  3.0
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Hello, world!

In this example, we set up a graph with three generators. Each of these generators operate on the same timer. Every time the timer fires, the generators produce a packet of data. The data they produce is dictated by the functors given to them at construction time. In this case, the functors are just functions that return strings.

The produced packets are then fed to an adder transformer node. This adder uses operator+= internally. Thus, for strings, it concatenates its input.

Finally, the adder's output is connected to an ostreamer. This node simply streams the data packets it receives to a std::ostream of our choice, std::cout in this case.

#include "flow.h"
#include "samples/math.h"
#include <chrono>
#include <iostream>
#include <string>
#include <thread>
using namespace std;
string hello()
return "Hello";
string space()
return ", ";
string world()
return "world!";
int main()
// Create a timer that will fire every three seconds.
flow::monotonous_timer mt(chrono::seconds(3));
// Instantiate a graph. It starts out empty.
// Include in the graph three generators, one with each function defined above.
auto sp_g1 = make_shared<flow::samples::generic::generator<string>>(mt, hello, "g1");
auto sp_g2 = make_shared<flow::samples::generic::generator<string>>(mt, space, "g2");
auto sp_g3 = make_shared<flow::samples::generic::generator<string>>(mt, world, "g3");
// Include an adder with three inputs.
auto sp_a1 = make_shared<flow::samples::math::adder<string>>(3, "a1");
// Include a consumer that just prints the data packets to std::cout.
auto sp_o1 = make_shared<flow::samples::generic::ostreamer<string>>(cout, "o1");
// Connect all three generators to the adder.
g.connect<string>(sp_g1, 0, sp_a1, 0);
g.connect<string>(sp_g2, 0, sp_a1, 1);
g.connect<string>(sp_g3, 0, sp_a1, 2);
// Connect the adder to the ostreamer.
g.connect<string>(sp_a1, 0, sp_o1, 0);
// Start the timer on its own thread so it doesn't block us here.
thread mt_t(ref(mt));
// Start the graph! Now we should see "Hello, world!" printed to the standard output every three seconds.
// Wait for some input. And when we get it...
char c;
cin >> c;
// ... pause the graph.
// Wait some more...
cin >> c;
// ...and re-start the graph.
// Wait some more...
cin >> c;
// ...and stop the graph completely.
// Stop the timer.
return 0;