Entering in an nth degree polynomial

Noah · 03-02-2006, 11:26 AM

For my Engineering Class I have to write a program that will take in an nth degree polynomial. The degree will always be positive and an integer. Then I have to use Simpson's Rule and the Rectangular rule to compare the numerical integration results, well... on to the point. I am having trouble with the entering of the polynomial. I don't know if I should have the subfunction be type void or not, because I am going to have most of my calculations done in subfunctions. Also I am unsure whether or not to have the user input the polynomial coefficients as a string or a character array. Any help or advice would be appreciated.

Code:

#include <stdio.h>
#include <stdlib.h>

void polynomial(char *);

main()
{

}

void polynomial(char *ptr)
{
	
	int degree;
	printf("\nEnter the degree of the polynomial you wish to integrate.");
	scanf("%d", &degree);
	ptr=(char *)malloc((degree+1) * sizeof(char));
	if(ptr= NULL)
	{
		puts("Memory Allocation Failed.");
	}

}

When I have

Code:

ptr=(char *)malloc((degree+1) * sizeof(char));

the degree+1 is for the entire length of the polynomial, for instance if you had a 2nd degree polynomial you would have 3 terms, x^2 + x + #.

Richie T · 03-02-2006, 09:02 PM

well what i would do is make your functions return the result of
the numerical integration - that way main can compare the two:
also you could use the maximum error calculation for simpsons
rule and see if the difference between the two methods is less
than it - just an aside. also, for reading in the coefficients, they're
gonna be integers, not chars - its not that easy to get a computer
to do calculations with variable names as opposed to numerical
values - dynamically allocate an array of ints, use a loop to
read in the correct coefficient into each element and then
implement your function - in my own opinion i would think it
better to enter the coefficients one by one. your output could
look like:

Code:

Enter degree: 2

Enter the coefficient of x^2: 1

Enter the coefficient of x: 0

Enter constant: 5

The polynomial is: x^2 + 5

getting output like that would be detailed (notice how it didn't
print x^1 and x^0? - just something i'd do if i had the time myself)

Good luck with implementing the numerical methods, hope i
answered your questions.

PS - you could avoid memory allocation and just define an array
large enough to store a reasonable number of coefficients - say
100. also, it wouldn't increase the complexity if you used double
for the coefficients, its up to you, but its always good to give a
user the freedom to enter in .87 if they so feel like it (and if the
same makes logical sense for the program of course!)

03-02-2006, 11:26 AM	#1
Noah Registered User Join Date: Mar 2006 Posts: 6	Entering in an nth degree polynomial For my Engineering Class I have to write a program that will take in an nth degree polynomial. The degree will always be positive and an integer. Then I have to use Simpson's Rule and the Rectangular rule to compare the numerical integration results, well... on to the point. I am having trouble with the entering of the polynomial. I don't know if I should have the subfunction be type void or not, because I am going to have most of my calculations done in subfunctions. Also I am unsure whether or not to have the user input the polynomial coefficients as a string or a character array. Any help or advice would be appreciated. Code: #include <stdio.h> #include <stdlib.h> void polynomial(char ); main() { } void polynomial(char ptr) { int degree; printf("\nEnter the degree of the polynomial you wish to integrate."); scanf("%d", &degree); ptr=(char )malloc((degree+1) sizeof(char)); if(ptr= NULL) { puts("Memory Allocation Failed."); } } When I have Code: ptr=(char )malloc((degree+1) sizeof(char)); the degree+1 is for the entire length of the polynomial, for instance if you had a 2nd degree polynomial you would have 3 terms, x^2 + x + #.
Noah is offline

03-02-2006, 09:02 PM	#2
Richie T The Richness... Join Date: Jan 2006 Location: Ireland Posts: 469	well what i would do is make your functions return the result of the numerical integration - that way main can compare the two: also you could use the maximum error calculation for simpsons rule and see if the difference between the two methods is less than it - just an aside. also, for reading in the coefficients, they're gonna be integers, not chars - its not that easy to get a computer to do calculations with variable names as opposed to numerical values - dynamically allocate an array of ints, use a loop to read in the correct coefficient into each element and then implement your function - in my own opinion i would think it better to enter the coefficients one by one. your output could look like: Code: Enter degree: 2 Enter the coefficient of x^2: 1 Enter the coefficient of x: 0 Enter constant: 5 The polynomial is: x^2 + 5 getting output like that would be detailed (notice how it didn't print x^1 and x^0? - just something i'd do if i had the time myself) Good luck with implementing the numerical methods, hope i answered your questions. PS - you could avoid memory allocation and just define an array large enough to store a reasonable number of coefficients - say 100. also, it wouldn't increase the complexity if you used double for the coefficients, its up to you, but its always good to give a user the freedom to enter in .87 if they so feel like it (and if the same makes logical sense for the program of course!) __________________ No No's: fflush (stdin); gets (); void main (); Goodies: Example of fgets (); The FAQ, C/C++ Reference My Gear: OS - Windows XP IDE - MS Visual C++ 2008 Express Edition ASCII stupid question, get a stupid ANSI
Richie T is offline

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