Max and Min is coming out as true instead of a number, what do I do?

Question

I need the minimum and maximum number out of an array but it is telling me that the address of function will always come out to true instead of a number. I can't figure out what to change.

#include <iostream>

using namespace std;

int main()
{
    double num1[10] {0.61, 1.70, 0.52, 1.34, 0.25, 1.20, 0.46, 1.10, 1.68, 1.37}; //material used in february
    double total1 {0};
    float average1 {0};
    int i;

    for (i=0; i<10; i++)
    {
        total1 = total1 + num1[i];
    }

    average1 = total1/10.0; //average of material used in feb

    double max1(double num1); // maximum of material used in feb

    double min1(double num1); // minimum of material used in feb

    cout << "Maximum is " << max1 << endl;
    cout << "Average is " << average1 << endl;
    cout << "Minimum is " << min1 << endl;


    double num2[10] {1.64, 1.15, 1.34, 1.63, 0.93, 0.51, 1.13, 1.16, 1.56, 1.38}; //material used in march
    double total2 {0};
    float average2 {0};
    int l;

    for (l=0; l<10; l++)
    {
        total2 = total2 + num2[l];
    }

    average2 = total2/10.0; //average of material used in march
    
    double max2(double num1); // maximum of material used in march

    double min2(double num1); // minimum of material used in march 

    cout << "Maximum is " << max2 << endl;
    cout << "Average is " << average2 << endl;
    cout << "Minimum is " << min2 << endl;

    return 0;

}

Your question has already been answered by J. Schultke below. As comment on the side, you have twice the same code. Please help yoruself and anybody wishing to look at your program by using a function that computes the min, max, and average from the numbers in your array. Also when asking questions, it helps to just include the minimum that illustrates your problem. — Tom, Aug 26 '20 at 09:45
I'm guessing that you were supposed to *implement* maximum and minimum functions, but misunderstood something about the exercise. — molbdnilo, Aug 26 '20 at 09:51

Jan Schultke · Accepted Answer · 2020-08-26T10:09:45.917

You are not printing a maximum here, you are printing a function pointer which is implicitly converted to bool. It is never nullptr, so it is true.

// These two lines are actually forward-declarations of two functions
// called max1 and min1.
double max1(double num1);
double min1(double num1);

cout << "Maximum is " << max1 << endl; // printing function pointer here
cout << "Average is " << average1 << endl;
cout << "Minimum is " << min1 << endl; // printing function pointer here

What you need instead is this:

#include <algorithm>
#include <numeric>
#include <array>

int main()
{
    constexpr std::array<double, 10> num1 {
        0.61, 1.70, 0.52, 1.34, 0.25, 1.20, 0.46, 1.10, 1.68, 1.37
    };

    double *max1 = std::max_element(std::begin(num1), std::end(num1));
    double *min1 = std::min_element(std::begin(num1), std::end(num1));
    double avg1 = std::accumulate(std::begin(num1), std::end(num1), 0.0)
                  / num1.size();

    // Note that we only need std::endl if we want to flush std::cout.
    // Otherwise '\n' is enough.
    std::cout << "Maximum is " << *max1 << '\n';
    std::cout << "Minimum is " << *min1 << '\n';
    std::cout << "Average is " << avg1 << '\n';

    // ...
}

std::min_element returns a pointer to the minimum in a range (in your case an array).

std::begin and std::end return iterators to the beginning and end of your array. This works with both std::array and C-style arrays.

Also note that std::accumulate can be used to compute the sum with ease. You don't need to write a loop for that yourself.

Also see Iterator = pointer? Or what is it? for more information on iterators and pointers and what the difference is.

Max and Min is coming out as true instead of a number, what do I do?

1 Answers1