/*
Author: Arun Somasundaram, CSE Dept, OSU

Simple program for namespaces.

A namespace is a mechanism for logical grouping.
A namespace is a scope.

*/

#include <iostream>

using namespace std;

namespace MathDataFunctions{
    
    float PI = 3.142;
    //Some Trivial Math Operations
    float add(float a, float b);
    float subtract(float a, float b);
    float addSubtract(float a, float b, float c); // a + b - c

    class ComplexNumber{
    private:
	float re, im;
    public:
	ComplexNumber(float r, float i){
	    re = r; im = i;
	    cout << "Complex Number ( " << re << ", " << im << " )" << endl;}
    };
    
}

float MathDataFunctions::add(float a, float b){
    return a + b;
}

float MathDataFunctions::subtract(float a, float b){
    return a - b;
}

float MathDataFunctions::addSubtract(float a, float b, float c){
    float d = add(a, b); //You don't need MathDataFunctions::add(a, b);
    return (d - c);
}

// A namespace is open. You can add names to it from several namespace declarations.
namespace MathDataFunctions{

    //Add multiply function to existing namespace
    float multiply(float a, float b){return a*b;}
    
}

namespace ClashWithMathDataFunctions{

    float subtract(float a, float b){return (b-a);}
    
}

int main(){
    
    cout << "Value of PI is " << MathDataFunctions::PI << endl;
    typedef MathDataFunctions::ComplexNumber MathComplex;
    MathComplex cNum1(10, 20);
    
    cout << MathDataFunctions::add(2, 3) << endl;
    cout << MathDataFunctions::subtract(2, 3) << endl;
    MathDataFunctions::ComplexNumber cNum2(100, 200);

    using MathDataFunctions::add; //using declaration
    cout << add(2, 3) << endl;
    //cout << subtract(2, 3) << endl; //Error why?
    
    using namespace MathDataFunctions;
    cout << add(2, 3) << endl; //After the using directive
    cout << subtract(2, 3) << endl; //After the using directive
    cout << multiply(2, 3) << endl; //After the using directive
    
    using ClashWithMathDataFunctions::subtract;

    cout << subtract(2, 3) << endl; //After the using declaration

    return 0;
    
}