Problem with functions returning a value.

[potatoeSalad]

I was hoping someone could tell me where I went wrong with this code i'm doing for school, the error message that keeps poping up says "undefined reference to getX(); and i don't know where to begin..Thanks a lot!!!

#include <cstdio>

void welcome();
void displayEqn(float a, float b, float c);
void displayResults(float X, float result);
float getX();

int main()
{
    welcome();

    float termA, termB, termC, result, X;

    printf(" Please enter the coefficient for the degree 2 term: ");
    scanf("%g", &termA);
    printf(" Please enter the coefficient for the degree 1 term: ");
    scanf("%g", &termB);
    printf(" Please enter the coefficient for the degree 0 term: ");
    scanf("%g", &termC);

    displayEqn(termA, termB, termC);

    result = (termA*X*X) + (termB*X) + (termC);
    
    X = getX();

    displayResults(X, result);


return 0;
}

void welcome()
{
    printf("You will be asked to enter the three!\n");
    printf("coefficients for a degree 2 polynomial. The equation");
    printf("will then be displayed and you will be given the");
    printf("opportunity to apply the polynomial to a data value.");
}


void displayEqn(float termA,float termB,float termC)
{
    printf("f(X) = %.2fX^2 + %.2fX + %.2f\n", termA, termB, termC);
}

void displayResults(float X, float result)
{
    printf("f(%.2f) = %.2f", X, result);
}

float getX(float X)
{
    printf("Please enter a value for X: ");
    scanf("%g", &X);

    return X;
}

[Locien]

float getX(float X) <-- remove the second "float X" and put it inside your function's { }.

[potatoeSalad]

Thanks! that definitely fixed the error message

[TheIdeasMan]

Another thing: scanf returns a value, you should make use of it to see whether the scanf worked. Not doing so is a recipe for a segmentation fault, or trying to use garbage or non-initialised variables.

If the scanf reads only one variable, you can use an if statement - a return value of 1 evaluates to true, 0 is false. If there is more than one being read in, then a switch might be better.

Good luck !!

[potatoeSalad]

Thanks for the reply! But this assignment is based on certain guidelines that the teacher has given.. and we're not at if statements yet lol.

I've gotten a bit further in the code but im now getting an error message saying "undefined reference to readCoeffs(float&, float&, float&)"..

I've played around with it cause it seems like a similar error to the previous one but still nothing..Thanks again for all the help!

#include <cstdio>

void welcome();
void displayEqn(float a, float b, float c);
void displayResults(float x, float result);
float getX();
void readCoeffs(float &a, float &b, float &c);
float calcResults(float a, float b, float c, float x);

int main()
{
    welcome();

    float a, b, c, result, x;
    displayEqn(a, b, c);
    readCoeffs(a, b, c);
    x = getX();
    result = calcResults(a, b, c, x);
    displayResults(x, result);


return 0;
}

void welcome()
{
    printf("You will be asked to enter the three \n");
    printf("coefficients for a degree 2 polynomial. The equation\n");
    printf("will then be displayed and you will be given the\n");
    printf("opportunity to apply the polynomial to a data value.\n");
}

void displayEqn(float a,float b, float c)
{
    printf("f(X) = %.2fX^2 + %.2fX + %.2f\n", a, b, c);
}

float calcResults(float a, float b, float c, float x)
{
    float result;
    result = (a*x*x) + (b*x) + (c);
}

void displayResults(float x, float result)
{
    printf("f(%.2f) = %.2f", x, result);
}

float getX()
{
    float x;
    printf("Please enter a value for X: ");
    scanf("%g", &x);

    return x;
}

void readCoeff(float &a, float &b, float &c)
{
    printf(" Please enter the coefficient for the degree 2 term: ");
    scanf("%g", &a);
    printf(" Please enter the coefficient for the degree 1 term: ");
    scanf("%g", &b);
    printf(" Please enter the coefficient for the degree 0 term: ");
    scanf("%g", &c);
}

[potatoeSalad]

Nevermind! I misplaced an s at the end of it

[potatoeSalad]

when i run the program, it seems good up until when it asks for a value for X..if i put it a 5 for X, the program says f(6.00) = 1.#R

Im not sure why this is happening, i've tried playing around with it for a while and can't seem to fix the problem..If anyone can please help with this, that would be awesome