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.

Quote:

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Originally Posted by skorman00

Code:

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  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:

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

---

won't print what you expect it to, while

Code:

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

---

probably will.

Quote:

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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.

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Or you could return a structure containing several variables.

Code:

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struct twofloats_t {
    float a, b;
};

---

Quote:

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Code:

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

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won't print what you expect it to, while

Code:

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

---

probably will.

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

Code:

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

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