Simple question regarding an equation inside of a function

Hey, so basically I have this issue, where I'm trying to put an equation inside of a function however it doesn't seem to set the value to the function and instead doesn't change it at all.

This is a predator prey simulation and I have this code inside of a for loop.

    wolves[i+1] = ((1 - wBr) * wolves[i] + I * S * rabbits[i] * wolves[i]); 
    rabbits[i+1] = (1 + rBr) * rabbits[i] - I * rabbits[i] * wolves[i];

When I execute this, it works as intended and changes the value of both of these arrays appropriately, however when I try to put it inside of a function,

    int calcRabbits(int R, int rBr, int I, int W)
{
     int x = (1 + rBr) * R - I * R * W;

    return x;
}

int calcWolves(int wBr, int W, int I, int S, int R)
{
    int x = ((1 - wBr) * W + I * S * R * R);
    return x;

}

And set the values as such

    rabbits[i+1] = calcRabbits ( rabbits[i], rBr, I, wolves[i]);
    wolves[i+1] = calcWolves(wBr, wolves[i], I, S, rabbits[i]);

The values remain the same as they were when they were initialized and it doesn't seem to work at all, and I have no idea why. I have been at this for a good few hours and it's probably something that I'm missing, but I can't figure it out.

Any and all help is appreciated.

Edit: I realized the parameters were wrong, but I tried it before with the correct parameters and it still didnt work, just accidentally changed it to the wrong parameters (Compiler mouse-over was showing the old version of the parameters)

Edit2: The entire section of code is this

    days = getDays(); // Runs function to get Number of days to run the simulation for
    dayCycle = getCycle(); // Runs the function get Cycle to get the # of days to mod by

    int开发者_如何学C wolves[days]; // Creates array wolves[] the size of the amount of days
    int rabbits[days]; // Creates array rabbits [] the size of the amount of days
    wolves[0] = W; // Sets the value of the starting number of wolves
    rabbits[0] = R; // sets starting value of rabbits


    for(int i = 0; i < days; i++) // For loop runs the simulation for the number of days
    {



//        rabbits[i+1] = calcRabbits ( rabbits[i], rBr, I, wolves[i]);    

// // //This is the code to change the value of both of these using the function 

//        wolves[i+1] = calcWolves(wBr, wolves[i], I, S, rabbits[i]);



    // This is the code that works and correctly sets the value for wolves[i+1]

        wolves[i+1] = calcWolves(wBr, wolves[i], I, S, rabbits[i]);
        rabbits[i+1] = (1 + rBr) * rabbits[i] - I * rabbits[i] * wolves[i];

    }

Edit: I realized my mistake, I was putting rBr and wBr in as ints, and they were floats which were numbers that were below 1, so they were being automatically converted to be 0. Thanks sje

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Phil I cannot see anything evidently wrong in your code.

My hunch is that your are messing up the parameters.

Using gdb at this point would be an over kill. I recommend you put print outs in calcRabbits and calcWolves. Print out all the parameters, the new value, and the iteration number. That will give you a good idea of what is going on and will help trace the problem.

Do you have the full code with initialization we could try to test and run?

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I'm not sure this is the problem, but this is bad:

int wolves[days]; // Creates array wolves[] the size of the amount of days
int rabbits[days]; // Creates array rabbits [] the size of the amount of days

days is determined at runtime. This is nonstandard in c++ (and for large number of days could destroy your stack) you should only be using constants in array sizes. You can dynamically size a vector to workaround this limitation (or heap allocate the array).

Change to this:

std::vector<int> wolves(days);
std::vector<int> rabbits(days);

Or to this:

int *wolves = new int[days];
int *rabbits = new int[days];

// all your code goes here

delete [] wolves;  // when you're done
delete [] rabbits;  // when you're done

Which will dynamically allocate the array on the heap. The rest of the code should work the same.

Don't forget to #include <vector>, if you use the vector approach.

If you're still having problems, I would cout << "Days: " << days << endl; to make sure you're getting the right number back from getDays(). If you got zero, it would seem to manifest itself in "the loop not working".

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I was using an integer as an argument for a double.