named-args-impl.cpp

#include <unordered_map>


struct NamedArguments {
	enum class Name {
		start, step, stop
	};

	struct BaseArg {
		Name name;
		NamedArguments operator=(int value) const {
			NamedArguments args;
			args.args[name] = value;
			return args;
		}
	};
	int get(Name n) {
		return args[n];
	}
	std::unordered_map<Name, int> args;
};

NamedArguments merge(NamedArguments a, const NamedArguments &b) {
	for (auto arg : b.args) {
		a.args[arg.first] = arg.second;
	}
	return a;
}

namespace name{
static const NamedArguments::BaseArg start{NamedArguments::Name::start};
static const NamedArguments::BaseArg stop{NamedArguments::Name::stop};
static const NamedArguments::BaseArg step{NamedArguments::Name::step};
};


void printNumbers(NamedArguments f1, NamedArguments f2, NamedArguments f3) {
	NamedArguments args = merge(merge(f1, f2), f3);

	int start = args.get(NamedArguments::Name::start);
	int stop = args.get(NamedArguments::Name::stop);
	int step = args.get(NamedArguments::Name::step);

	for (int c = start; c < stop; c += step) {
		std::cout << c << ' ';
	}
	std::cout << std::endl;
}


int main() {
	printNumbers(name::start = 0, name::stop = 10, name::step = 1);
	printNumbers(name::stop = 55, name::start = 5, name::step = 5);
	return 0;
}