Thread: Trying to understand this homework

We're learning about C Functions right now, however I'm not exactly sure what my homework is asking for....

Here's the problem:

I think it is asking for a program that will calculate a running total where each element is tossed inside the exponent function and spit out into the adding program.

Code:

int polyTermToValue(int coefficient, int variable, int exponent) {
	int value;
 
	// calculations on value
 
	return value;
}
 
int mainStuff() {
	int coefficient = 0;
	int variable = 0;
	int exponent = 0;
	int sum = 0;
	int sentinel = 1;
	while (sentinel) {
		// ask user for coefficient, variable, exponent or ask user to enter sentinel
		sum += polyTermToValue(coefficient, variable, exponent);
	}
 
	// sum is found.  do what you want with it.
}

In the formula 'a' can be different for each term. Think of your formula as something like: 12x⁴ + 2x³ + x² + 6x² + 33. You need to supply the correct "a" value for each term and then do the multiplications required.

Jim

Yeah, so I figured out that you need to ask the user for inputs for the highest exponent, coefficients, and the value of X. You then need to calculate the function for user inputted X (coeffiecient(x)^exp) from the highest exponent to 0.

Ex: 2x^3 + 3x^2 + 6x^1 + 2x^0

Not sure how I'd do that, I have a start, but not sure where to go from next.

Code:

#include <stdio.h>


int polynomial();
int expon, valx, coeff, a;


void main(){
    printf("Enter the highest exponent of your polynomial\n");
	scanf("%d", expon);
	
	printf("\nEnter the value of x");
	scanf("%d", valx);
	
	printf("\nEnter %d coefficients", expon+1);
}


int polynomial(){


	int expon, valx, coeff, a;
	int myArray[100];
	
	
	printf("Enter the highest exponent of your polynomial\n");
	scanf("%d", expon);
	
	printf("Enter the value of x\n");
	scanf("%d", valx);
	
	printf("Enter %d coefficients\n", expon+1);
	
	
	for(int i=0; i<expon; i++){
		scanf("%d", coeff);
		myArray[i] = coeff;
	for(int j=0; j<expon; j++){
		a = myArray[i];
		myArray[i] = myArray[i+1];
		myArray[i+1] = a;
	}
	}
	
	
	for(int i=0; i<expon; i++){
		a = myArray[i];
		myArray[i] = myArray[i+1];
		myArray[i+1] = a;
	}
     


      
}

Any ideas? Updated code:

Code:

#include <stdio.h>


int polynomial();
int expon, valx, coeff, a;


void main(){
   printf("The answer to your polynomial is %d\n ", polynomial());
}


int polynomial(){


int xval, expo, coeff; //declare values
int i, sum; // loop tracker/sum(total value)


int myArray[1000]; // Array declaration


printf("Please enter an x-value\n"); //scanning in x-value
scanf("%d", xval);


printf("Please enter the highest power of the exponent\n"); // Scan in highest exponent
scanf("%d", expo);




for (i = 0; i < expo; i++){
    printf("Please enter a coefficient\n");
	scanf("%d", coeff);
	coeff = myArray[i];
	//scan in coefficients using array
}
for (i = 0; i < expo; i++){
    xval = xval * xval;
}


for(i = 0; i < expo; i++){
    xval = xval * myArray[i];//take xval and multiply it by the coefficient
    sum += myArray[i]; //add that to the sum
}


return sum;


}

Any ideas?

Perhaps you should re-read your instructions?

Write one function definition which takes the coefficient (a_i), variable (x), and exponent of the variable (in the term) as parameters.

Where is this function that you will call for every term in the equation?

Jim

It's all inside the function polynomial()

I need to do all of the math and return the value of (a, x and the exponent) in F(X).

The value returned should be an integer. I don't need to show the polynomial.

I think the teacher wants something a little different than figuring it all out in polynomial().

Code:

input a
input x
input E
double F_x = a;
while (E > 0) {
   F_x += CalculateTerm(a, x, E--);
}
print F_x

Originally Posted by whiteflags

I think the teacher wants something a little different than figuring it all out in polynomial().

Code:

input a
input x
input E
double F_x = a;
while (E > 0) {
   F_x += CalculateTerm(a, x, E--);
}
print F_x

I'm afraid I don't follow. There are terms "a*x^e". I think the function is supposed to calculate each term and then I'm supposed to call it as many times as the user inputted exponents (plus 1 for x^0)... I'm not sure how I'd go about doing that.

I'm assuming the While loop is to call the function as many as times as exponents the user inputted.

The idea is that the highest exponent is also the number of times that you need to call the function that calculates terms. So if you write a function that can compute any one term, you end up with code similar to what I suggested.

CalculateTerm(a,x,5) for example would return ax^5 to you, you add it to F_x, then you do the 4th power term, etc.

By the way, I just noticed that there is a divide by zero possibility in the code I wrote that should be fixed with an if statement in the logToValue function.