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I'm a newbie at posting code so I'm sorry if I make any mistakes. The 26 line won't let me compile and I don't understand why. can anyone help me???

#include <iostream>
#include <iomanip>
using namespace std;

double population(double pop, double birthRate, double deathRate);
 void printPopulations(
  double startPop, double birthRate, double deathRate, int numYears);


	double population(double pop, double birthRate, double deathRate)
    {

double n = 0;

n = pop + (birthRate*pop) - (deathRate*pop);

return n;

}

void printPopulations(double startPop, double birthRate, double deathRate, int numYears)
{

for ( int i = 0 ; i < numYears ; i++ )
{
startPop = population (double birthRate, double deathRate, numYears, double n);
cout << "For year " << i+1 << " the population is " << startPop << endl ;
}

}



int main()
{
        double startPop,          
              birthRate,        
              deathRate;       
        int   numYears;         

        
        cout << "This program calculates population change.\n";
        cout << "Enter the starting population size: ";
        cin  >> startPop;
        while (startPop < 2.0)
        {
                cout << "Starting population must be 2 or more.  Please re-enter: ";
                cin  >> startPop; 
        }

        
        cout << "Enter the annual birth rate (as % of current population): ";
        cin  >> birthRate;
        while (birthRate < 0)
        {
                cout << "Birth rate percent cannot be negative.  Please re-enter: ";
                cin  >> birthRate;
        }

        birthRate = birthRate / 100;     

        cout << "Enter the annual death rate (as % of current population): ";
        cin  >> deathRate;
        while (deathRate < 0)
        {
                cout << "Death rate percent cannot be negative.  Please re-enter: ";
                cin  >> deathRate;
        }

        deathRate = deathRate / 100;     

        cout << "For how many years do you wish to view population changes? ";
        cin  >> numYears;
        while (numYears < 1)
        {
                cout << "Years must be one or more. Please re-enter: ";
                cin  >> numYears;
        }

        printPopulations(startPop, birthRate, deathRate, numYears);
        system ("pause");
        return 0;
}
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Last Post by Nick6425fl
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In line 26 this:

population (double birthRate, double deathRate, numYears, double n);

is a function declaration, not a function call. Function calls don't list argument types, just argument names or argument values.

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I'm still learning about all of this...I'm sure when I look back at this post in a couple of months I'll laugh. Thanks for the reply, but what do you think that line should exactly be to make that code work?

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I'm still learning about all of this...I'm sure when I look back at this post in a couple of months I'll laugh. Thanks for the reply, but what do you think that line should exactly be to make that code work?

If you format/indent your code, it'll be much easier to follow. To answer your question, I can recommend something that will be a proper function call, but it doesn't make any sense here. I think you need to take a step back and decide what you are trying to do.

This is a function call:

startPop = population (startPop, birthRate, deathRate);

I doubt that is what you want, but it is a legal function call.

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If you format/indent your code, it'll be much easier to follow. To answer your question, I can recommend something that will be a proper function call, but it doesn't make any sense here. I think you need to take a step back and decide what you are trying to do.

This is a function call:

startPop = population (startPop, birthRate, deathRate);

I doubt that is what you want, but it is a legal function call.

That fixed it! Next time I post I'll indent to make it easier to read. Thank you again Vernon.

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