Quadratic Function

Hello all,
I want to rewrite the quadratic equation as a function and as a function in the main. Below are the two programs but was not giving accourate answer.

For the function alone:

Code:

float quadratic(float x1, float x2)
{
   float a, b, c, d, g, h=0.0;
   printf ("\nEnter value for a\n");
   scanf ("%f", &a);
   printf ("\nEnter value for b\n");
   scanf ("%f", &b);
   printf ("\nEnter value for c\n");
   scanf ("%f", &c);
   d=sqrt((b*b)-4*a*c);
   g=2*a;
   if (g==h)
   {
     printf ("\nYou have performed an illegal operation as the divisor cannot be zero.");
   }
   else
   {
     x1=(-b+d/g); 
     x2=(-b-d/g); 
     printf ("\nFirst real root is," x1);
     printf ("\nSecond real root is," x2);
   }
   return (x1, x2);
}

it was not printing any values neither showing any calculations done

The second one that has main with it

Code:

/* program to calculate the root of a quadratic equation*/
#include <stdio.h>
#include <math.h>

float quadratic(float a, float b, float c)
{
   float d, g, h=0.0, x1;
   g=2*a;
   if (g==h)
   {
     printf ("\nYou have performed an illegal operation as the divisor cannot be zero.");
   }
   else
   {
     x1=(-b+((b*b)-4*a*c))/g; 
   }
   return (x1);
}

float quadratic1(float a, float b, float c)
{
   float d, g, h=0.0, x2;
   g=2*a;
   if (g==h)
   {
     printf ("\nYou have performed an illegal operation as the divisor cannot be zero.");
   }
   else
   {
     x2=(-b-((b*b)-4*a*c))/g; 
   }
   return (x2);
}
main()
{
   float a, b, c, x1, x2;
   printf ("\nEnter value for a\n");
   scanf ("%f", &a);
   printf ("\nEnter value for b\n");
   scanf ("%f", &b);
   printf ("\nEnter value for c\n");
   scanf ("%f", &c);
   x1 = quadratic(a,b,c);
   x2 = quadratic1(a,b,c);
   printf("\na=%f,", a);
   printf("\nb=%f,", b);
   printf("\nc=%f,", c);
   printf("\nThe real roots are %f, %f", x1, x2);
}

Please help me out.

Code:

  return (x1, x2);

Don't return 2 values. I would suggest returning 0 as well.

You're program ends when main ends, closing the window before you can see anything. you can use getch() to pause it until a key is pressed.

Originally Posted by skorman00

Code:

  return (x1, x2);

Don't return 2 values. I would suggest returning 0 as well.

You're program ends when main ends, closing the window before you can see anything. you can use getch() to pause it until a key is pressed.

It doesnt have a main function, it is just a user-defined function, also i want it to print out the result but was not doing that.

[QUOTE=abs.emailverify]

Code:

float quadratic(float x1, float x2)
{
   float a, b, c, d, g, h=0.0;
   printf ("\nEnter value for a\n");
   scanf ("%f", &a);
   printf ("\nEnter value for b\n");
   scanf ("%f", &b);
   printf ("\nEnter value for c\n");
   scanf ("%f", &c);
   d=sqrt((b*b)-4*a*c);
   g=2*a;
   if (g==h)
   {
     printf ("\nYou have performed an illegal operation as the divisor cannot be zero.");
   }
   else
   {
     x1=(-b+d/g); 
     x2=(-b-d/g); 
     printf ("\nFirst real root is," x1);
     printf ("\nSecond real root is," x2);
   }
   return (x1, x2);
}

it was not printing any values neither showing any calculations done

Here's the 2 things that are wrong :

1) A function in C can't return a tuple. You'd have to return a float pointer if you actually want to return both those answers.

2) There's a reason you aren't seeing any calculation being done, namely that

Code:

printf ("\nFirst real root is," x1);

won't print what you expect it to, while

Code:

printf ("\nFirst real root is, %f" x1);

probably will.

1) A function in C can't return a tuple. You'd have to return a float pointer if you actually want to return both those answers.

Or you could return a structure containing several variables.

Code:

struct twofloats_t {
    float a, b;
};

Code:

printf ("\nFirst real root is," x1);

won't print what you expect it to, while

Code:

printf ("\nFirst real root is, %f" x1);

probably will.

It probably won't, unless you add a comma too.

Code:

printf ("\nFirst real root is, %f", x1);

If a = 0, the the 1 root is given by -c/b.