complex number calculator in c using functions and structs - c

Question

Kind of a continuation of my last post, I'm trying to write a complex number calculator using structs and functions. My program has to have a function for reading in complex numbers from user input, and it has to have another function for adding them. This is the function prototype I was given:
Complex read_complex(void)
This is the prototype I have to use and it can't be changed. Right now I'm trying trouble passing the values I scan in from the above function into my function for adding the complex numbers. This is my code:
#include <stdio.h>
#include <math.h>
#include<string.h>
typedef struct Complex_ {
double RealPart;
double ImagPart;
} Complex;
Complex read_complex(void);
Complex add_complex(Complex z1, Complex z2);
Complex mul_complex(Complex z1, Complex z2);
int main(void) {
char ent[50];
Complex user1, user2;
printf("Enter Add for addition, Mult for multiplication, MA for magnitude and angle, or Exit to quit: ");
scanf("%s", ent);
if (ent[0] == 'A') {
read_complex();
add_complex(user1, user2);
}
else if (ent[0] == 'M' && ent[1] == 'u') {
read_complex();
mul_complex(user1, user2);
}
else if (ent[0] == 'M' && ent[1] == 'A') {
read_complex();
}
else {
}
return(0);
}
Complex read_complex(void) {
Complex* user1;
Complex* user2;
printf("Enter first complex number: ");
scanf("%lf %lf", &user1->RealPart, &user1->ImagPart);
printf("Enter the second complex number: ");
scanf("%lf %lf", &user2->RealPart, &user2->ImagPart);
return;
}
Complex add_complex(Complex z1, Complex z2) {
Complex z3;
z3.RealPart = z1.RealPart + z2.RealPart;
z3.ImagPart = z1.ImagPart + z2.ImagPart;
printf("(%lf + %lfi) + (%lf + %lfi) = %lf + %lfi", z1.RealPart, z1.ImagPart, z2.RealPart, z2.ImagPart, z3.RealPart, z3.ImagPart);;
return(z3);
}
Complex mul_complex(Complex z1, Complex z2) {
Complex z3;
z3.RealPart = z1.RealPart * z2.RealPart;
z3.ImagPart = z1.ImagPart * z2.ImagPart;
return(z3);
}
(Large parts of the code are incomplete right now because I'm just trying to figure out the adding part). The current problem I'm having is that when I run the code, I get an error saying the user1 and user2 variables are uninitialized, and I don't know how to initialize struct variables.

Answer 1

You seem to have a misunderstanding of how pointers work.
The way you've written read_complex, you seem to think that the pointers user1 and user2 in this function automatically refer to the variables of the same name in the main function. That's not how C works.
What you actually have is two uninitialized pointers inside of read_complex that you then attempt to dereference via the -> operator. You're also not returning anything from this function even though it's declared to do so.
This function is supposed to return a single copy of a Complex, so you should create one locally, read the values into it, then return it. The return value should then be assigned to a local variable. So this also means you need to call this function for each Complex you read.
Also, you may want to review how to multiply complex numbers.

Answer 2

This is the function prototype I was given: Complex read_complex(void) This is the prototype I have to use and it can't be changed.
read_complex() returns 1 object of type Complex. Use it to read 1, not 2, complex numbers.
Let use use that function to read and also create another function that calls it to read 2 complex numbers.
// Receive the address of 2 objects,
// so this code knows where to save the result.
void read_complex2(Complex *a, Complex *b) {
printf("Enter first complex number: ");
*a = read_complex();
printf("Enter the second complex number: ");
*b = read_complex();
}
read_complex()
read_complex() becomes simple: read 2 double. Check results.
Complex read_complex(void) {
Complex x;
if (scanf("%lf %lf", &x.RealPart, &x.ImagPart) != 2) {
fprintf(stderr, "Invalid input.\n");
exit(EXIT_FAILURE);
}
return x;
}
main()
Adjust like:
if (ent[0] == 'A') {
//read_complex();
read_complex2(&user1, &user2);// Pass in addresses of objects.
add_complex(user1, user2);
...