Trouble with variables

[DN7SE3v7]

In the code below, the first function gets input from the user and the second function is suppose to do some calculation and display an answer. However, I keep getting "-1.#NID" where the answer should be. Please help.

#include <iostream>
#include <string>
using namespace std;
double current_price, past_price;
void get_input(double current_price,double past_price);
void display_results(double current_price, double past_price);

int main()
{
	string answer;
    do
	{
	get_input(current_price, past_price);
	display_results(current_price, past_price);
	cout << "\n";
	cout << "Run the program again?(Type Yes or No.)\n";
        cin >> answer;
	}while(answer == "Yes" || answer == "yes");
}
void get_input(double current_price, double past_price)
{
    cout << "Please enter the current price of an item:\n";
    cin >> current_price;
    cout << "Please enter the past price of an item\n";
    cin >> past_price;
}
void display_results(double current_price, double past_price)
{
    double rate_of_inflation = (current_price - past_price)/past_price;
    cout << "The rate of inflation is: " << rate_of_inflation << "%\n";
    cout << "The estimated price in a year is: $" << (rate_of_inflation * current_price) + current_price;
}

[koopey]

while calling the get_input function, the arguement "current_price" and 'past_price' are not yet initilized(they don't exist yet). so you cant use them as arguement to call the function:

in do function

do
	{

	cout << "Please enter the current price of an item:\n";
    cin >> current_price;
    cout << "Please enter the past price of an item\n";
    cin >> past_price;
    display_results(current_price, past_price);
	cout << "\n";
	cout << "Run the program again?(Type Yes or No.)\n";
        cin >> answer;
	}while(answer == "Yes" || answer == "yes");

and delete the get_input function. should work like a charm.

[DN7SE3v7]

One of the constraints of my assignment is to use a function to get the user input.

[koopey]

well, in that case you could use either a pointer or just function inside a function. I am just guessing that you haven't reached to pointer yet. so another way it is;

#include <iostream>
#include <string>
using namespace std;
double current_price, past_price;
void get_input();
void display_results(double current_price, double past_price);

int main()
{
	string answer;
    do
	{
	get_input();

	cout << "\n";
	cout << "Run the program again?(Type Yes or No.)\n";
        cin >> answer;
	}while(answer == "Yes" || answer == "yes");
}
void get_input()
{
    cout << "Please enter the current price of an item:\n";
    cin >> current_price;
    cout << "Please enter the past price of an item\n";
    cin >> past_price;
    display_results(current_price, past_price);
}
void display_results(double current_price, double past_price)
{
    double rate_of_inflation = (current_price - past_price)/past_price;
    cout << "The rate of inflation is: " << rate_of_inflation << "%\n";
    cout << "The estimated price in a year is: $" << (rate_of_inflation * current_price) + current_price;
}

[koopey]

oh, i didn't see that you had declared a global variable there. then it is easier without use of pointer:

in your original program, make these changes:

void get_input();///line number 5 in your original program

get_input(); /// in line 13;

void get_input()///in line 20 

that's it:

[DN7SE3v7]

Thank you so much. Such a simple fix and I couldn't even see it.

[Little Bobby Tables]

@koopey
- they arent initialized, but they do exist. i dont know who told you they dont.
- you can use unitialized variables in an argument
- do is not a loop

@op: using namespace std; and global variables are bad. i suggest looking into passing by reference instead of global variables.

[koopey]

@Little Bobby Tales
- I meant to say that they don't contain the value that we want, just random number is stored in the memory of the variable. I used

they don't exist

in kind of literary sense to make it easier to understand and didn't realize 'exist' could be perceived in other ways.(which i now realize are true and more plausible)

- I don't understand how 'do' is not a loop(among others as while and for)

- continued program using global variable feeling that OP wanted it that way for sake of convenience.

- I didn't know using namespace std is bad practice. I use jumping into c++ and same is used in every of its sample program, at least till now.

[Little Bobby Tables]

im sorry... i meant do is not a function referring to:

in do function

same is used in every of its sample program, at least till now.

this is true unfortunately, but its very bad practice