Structs and Unions + Randoms Got me down

[mixelplik]

This code is supposed to randomly assign numbers to an array of structs, but isn't working at all.

I have no clue why, everything looks fine to me, can some one take a look and tell me why it's crapping out on me?

#include <iostream>
#include <cmath>
#include <cstdlib>
#include <ctime>

using namespace std;
enum Type{Even, Odd};
const string TypeString[2] = {"even","odd"};

// ------ Structures ---------------------------------------------

union Value
{
    int i;
    double d;
};

struct Number
{
    Type type;
    Value value;
};

// ------ Prototypes ---------------------------------------------
Number assign(Number);
void print(Number);



// ****** MAIN ***************************************************
int main()
{
//    srand(time(0));
    Number var[10];

    for (int i = 0; i < 10; i++)
        assign(var[i]);

    for (int i = 0; i < 10; i++)
        print(var[i]);

    for (int i = 0; i < 10; i++)
                cout << var[i].value.d << endl;
    return 0;
}

// ****** FUNCTION: Print ****************************************
//
//****************************************************************
void print(Number input)
{
    if(input.type == Even)
    {
        cout << "The number is " << TypeString[input.type] << " " << input.value.i << endl;
    }
    else if(input.type == Odd)
    {
        cout << "The number is " << TypeString[input.type] << " " <<input.value.d << endl;
    }

    return;
}

// ****** FUNCTION: Assign ***************************************
//
//****************************************************************
Number assign(Number input)
{
    int num;

    num = rand() % 10 + 1;

    if(num % 2 == 0)
    {
        input.type = Even;
        input.value.i = num;
    }
    else  if(num % 2 != 0)
    {
        input.type = Odd;
        input.value.d =num;
    }


    return input;
}

Ouput
The number is even 2686652
The number is even 4286736

Process returned 0 (0x0) execution time : 0.062 s
Press any key to continue.

As you can see, it's only printing twice instead of 10 times, and the numbers are way nutz. Also, I'm using srand, but getting the same values everytime it runs.

[Ancient Dragon]

You need to pass Number to assign() by reference, not by value so that assign() can change the structure that is declared in main().

[mike_2000_17]

Your assign function takes the parameter by value which means that it creates a local copy of the passed variable and changes only that. If you want the changes made in the assign function to be reflected on the variable passed to it, you need to take the parameter by reference. As so:

void assign(Number& );

//....


void assign(Number& input)
{
    int num;
    num = rand() % 10 + 1;
    if(num % 2 == 0)
    {
        input.type = Even;
        input.value.i = num;
    }
    else  if(num % 2 != 0)
    {
        input.type = Odd;
        input.value.d =num;
    }
}

Notice the ampersand & added to the parameter type, this signifies that the parameter is taken by reference (referring to the variable passed to the function).

Also, I'm using srand, but getting the same values everytime it runs.

Your use of srand is commented out of the code. If you comment it back in, it should work:

srand((unsigned int)time(0));

You do it correctly, i.e., calling it only once at the start of the program and seeding it with a often-changing value (e.g., current time).

[mixelplik]

Thank you! I had arrays and pointers on my brain and was treating structures as such. Thanks, you guys are so great!