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square equation_new.cpp
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square equation_new.cpp
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#include <stdio.h>
#include <math.h>
#include <assert.h>
#include <stdlib.h>
#define UNDEF_ROOT -1
#define BORDER 1e-20
//-----------------------------------------------------------------------------
//! Solves a square equation ax2+bx+c = 0
//! @param [in] a a - coefficient
//! @param [in] b b - coefficient
//! @param [in] c c - coefficient
//! @param [out] x1 Pointer to the first root
//! @param [out] x2 Pointer to the second root
//!
//! return number of roots
//!
//! in case of infinite number of roots,
//! returns UNDEF_ROOT.
//-----------------------------------------------------------------------------
int Eq_Sol (double a, double b, double c,
double* x1, double* x2);
//-----------------------------------------------------------------------------
//! Print roots of equation
//! @param [in] Num_Roots
//! @param [in] x1
//! @param [in] x2
//!
//!
//! in case of infinite number of roots,
//! returns UNDEF_ROOT.
//-----------------------------------------------------------------------------
void Solution_Checker();
void Print_Roots (int Num_Roots, double x1, double x2);
//-----------------------------------------------------------------------------
int main()
{
Solution_Checker();
return 0;
printf("Square equation solver\n");
printf("Enter a, b, c: ");
double a = 0, b = 0, c = 0;
int GoodRead = 0;
do
{
printf("Enter a, b, c: ");
GoodRead = scanf ("%lg %lg %lg", &a, &b, &c);
fflush(stdin);
}while (GoodRead != 3);
double x1 = 0, x2 = 0;
int Num_Roots = Eq_Sol (a, b, c, &x1, &x2);
Print_Roots(Num_Roots, x1, x2);
return 0;
}
int Eq_Sol (double a, double b, double c,
double* x1, double* x2)
{
assert(isfinite(a));
assert(isfinite(b));
assert(isfinite(c));
assert(x1 != NULL);
assert(x2 != NULL);
assert(x1 != x2);
if (BORDER >= a && a >= -BORDER)
{
if (BORDER >= b && b >= -BORDER)
{
return (BORDER >= c && c >= -BORDER) ? UNDEF_ROOT: 0;
}
else
{
*x1 = *x2 = -c / b;
return 1;
}
}
else
{
double D = b*b - 4*a*c;
if (BORDER >= D && D >= -BORDER)
{
*x1 = *x2 = -b / (2*a);
return 1;
}
else if(D <= -BORDER)
return 0;
else
{
*x1 = (-b + sqrt(D)) / (2*a);
*x2 = (-b - sqrt(D)) / (2*a);
return 2;
}
}
}
void Solution_Checker()
{
double x1 = 0, x2 = 0;
#define CHECKER \
if ((Eq_Sol (a, b, c, &x1, &x2)) != exp_Num_Roots || x1 != exp_x1 || x2 != exp_x2) \
printf("Error, false roots (a = %d, b = %d, c = %d)\n", a, b, c); \
else \
{ \
printf("True\n"); \
x1 = x2 = 0; \
}
int exp_Num_Roots = 2;
double exp_x1 = -1;
double exp_x2 = -2;
int a = 1;
int b = 3;
int c = 2;
CHECKER;
exp_Num_Roots = 1;
exp_x1 = -0.5;
exp_x2 = -0.5;
a = 4;
b = 4;
c = 1;
CHECKER;
exp_Num_Roots = 0;
exp_x1 = 0;
exp_x2 = 0;
a = 2;
b = 1;
c = 5;
CHECKER;
exp_Num_Roots = UNDEF_ROOT;
exp_x1 = 0;
exp_x2 = 0;
a = 0;
b = 0;
c = 0;
CHECKER;
}
void Print_Roots (int Num_Roots, double x1, double x2)
{
assert(isfinite(x1));
assert(isfinite(x2));
switch (Num_Roots)
{
case 0: printf ("No roots\n");
break;
case 1: printf ("x = %lg", x1);
break;
case 2: printf ("x1 = %lg\nx2 = %lg\n", x1, x2);
break;
case UNDEF_ROOT: printf ("Any number\n");
break;
default: printf ("Error: Num_Roots = %d", Num_Roots);
break;
}
}
//-----------------------------------------------------------------------------