main.cpp

// Copyright BDH Lab 2018
#include <iostream>
#include <string>

using std::cout;
using std::string;

// IO class
class IO {
    string output;
 public:
    void setOutput(string output) {
        this->output = output;
    }

    string getOutput() {
        return this->output;
    }

    IO bind(IO io) {
        IO binded;
        binded.setOutput(this->output + io.getOutput());
        return binded;
    }

    void execute() {
        cout << output;
    }
};

// IO text
IO text(string text) {
    IO io;
    io.setOutput(text);

    return io;
}

// Functional core's main
IO main_() {
    return text("Hello World!\n")
        .bind(
            text("Hi hi!\n"));
}

// Imperative shell's main
int main() {
    main_().execute();

    return 0;
}