Lesson: Structure, task 1

# include <stdio.h>

void fn_add (float x1, float x2, float y1, float y2, float *res_x, float *res_y);
void fn_sub (float x1, float x2, float y1, float y2, float *res_x, float *res_y);
void fn_mul (float x1, float x2, float y1, float y2, float *res_x, float *res_y);
void fn_div (float x1, float x2, float y1, float y2, float *res_x, float *res_y);

main (void)
{
        struct compl {
                float x;
                float y;
        };
        struct compl z1, z2, res;
        float *zx, *zy;
        int op;
        zx=&res.x;
        zy=&res.y;
        while (1) {
                op=5; // quit by default
                z1.x=z1.y=z2.x=z2.y=0;
                printf ("1. Add\n2. Substract\n3. Multiplication\n4. Division\n5. Quit\nPlese select operation: ");
                scanf ("%d", &op);
                if ((op>=1)&&(op<=4)) {
                        printf ("\nPlease input real part of first complex value: ");
                        scanf ("%f", &z1.x);
                        printf ("\nPlease input imaginary part of first complex value: ");
                        scanf ("%f", &z1.y);
                        printf ("\nPlease input real part of second complex value: ");
                        scanf ("%f", &z2.x);
                        printf ("\nPlease input imaginary part of second complex value: ");
                        scanf ("%f", &z2.y);
                        if ((z2.x==0)&&(z2.y==0)&&(op==4)) {
                                printf ("\nDivision by zero is impossible\n\n");
                        } else {
                                switch (op) {
                                        case 1: fn_add (z1.x, z2.x, z1.y, z2.y, zx, zy); break;
                                        case 2: fn_sub (z1.x, z2.x, z1.y, z2.y, zx, zy); break;
                                        case 3: fn_mul (z1.x, z2.x, z1.y, z2.y, zx, zy); break;
                                        case 4: fn_div (z1.x, z2.x, z1.y, z2.y, zx, zy); break;
                                }
                                printf ("\nResult z=(%2.2f, %2.2f)\n\n", res.x, res.y);
                        }
                } else if (op==5) {
                                break;
                }
        }
}

void fn_add (float x1, float x2, float y1, float y2, float *res_x, float *res_y)
{
        *res_x=x1+x2;
        *res_y=y1+y2;
}

void fn_sub (float x1, float x2, float y1, float y2, float *res_x, float *res_y)
{
        *res_x=x1-x2;
        *res_y=y1-y2;
}

void fn_mul (float x1, float x2, float y1, float y2, float *res_x, float *res_y)
{
        *res_x=x1*x2-y1*y2;
        *res_y=x2*y1+x1*y2;
}

void fn_div (float x1, float x2, float y1, float y2, float *res_x, float *res_y)
{
        *res_x=(x1*x2+y1*y2)/(x2*x2+y2*y2);
        *res_y=(y1*x2-x1*y2)/(x2*x2+y2*y2);
}