Hey there! Let's work through your two core issues and get that complex calculator on track. The problems stem from a misinterpretation of how the read_complex function should work, plus some struct variable handling mistakes. Here's how to fix everything step by step:

1. Fix the read_complex function (and its purpose) #

The given prototype Complex read_complex(void) tells us this function should read a single complex number from input and return it — not two at once. Your current implementation uses uninitialized pointers (Complex* user1; and Complex* user2;), which is why you're getting "uninitialized variable" errors (those pointers point to random memory, accessing them causes undefined behavior like crashes or garbage values).

Here's the corrected, working version of read_complex:

Complex read_complex(void) {
    Complex num; // Declare a local Complex variable (no pointers needed here!)
    printf("Enter complex number (real part followed by imaginary part): ");
    scanf("%lf %lf", &num.RealPart, &num.ImagPart);
    return num; // Return the fully populated struct
}

2. Pass read values to your math functions (and fix uninitialized variables) #

In main(), you declared user1 and user2 but never assigned them any values — that's exactly why you're seeing the "uninitialized variable" error. When you call read_complex(), you need to capture its return value and store it in these variables. For example, when handling addition:

if (strcmp(ent, "Add") == 0) { // Use strcmp() instead of checking first characters — way more reliable!
    user1 = read_complex(); // Assign first input complex number to user1
    user2 = read_complex(); // Assign second input complex number to user2
    add_complex(user1, user2); // Now pass initialized variables to the addition function
}

3. Bonus fixes for small bugs #

• In main(), checking ent[0] == 'A' is fragile (what if the user types "add" lowercase?). Use strcmp() with full string literals to avoid case-sensitive or partial-match bugs.
• Your original mul_complex function uses incorrect math for complex multiplication. The correct formula is:

  (a + bi) * (c + di) = (ac - bd) + (ad + bc)i
  

  I've fixed this in the full code below.
• Your original read_complex had no return statement (a compiler error) — the corrected version fixes this.

Full corrected code (focused on working addition first) #

#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 (strcmp(ent, "Add") == 0) {
        user1 = read_complex();
        user2 = read_complex();
        add_complex(user1, user2);
    } else if (strcmp(ent, "Mult") == 0) {
        user1 = read_complex();
        user2 = read_complex();
        Complex result = mul_complex(user1, user2);
        printf("(%.2lf + %.2lfi) * (%.2lf + %.2lfi) = %.2lf + %.2lfi\n",
               user1.RealPart, user1.ImagPart, user2.RealPart, user2.ImagPart,
               result.RealPart, result.ImagPart);
    } else if (strcmp(ent, "MA") == 0) {
        user1 = read_complex();
        // Add magnitude/angle calculation code here later
    } else if (strcmp(ent, "Exit") == 0) {
        printf("Exiting program.\n");
    } else {
        printf("Invalid command — please try again.\n");
    }
    
    return 0;
}

Complex read_complex(void) {
    Complex num;
    printf("Enter complex number (real imaginary): ");
    scanf("%lf %lf", &num.RealPart, &num.ImagPart);
    return num;
}

Complex add_complex(Complex z1, Complex z2) {
    Complex z3;
    z3.RealPart = z1.RealPart + z2.RealPart;
    z3.ImagPart = z1.ImagPart + z2.ImagPart;
    printf("(%.2lf + %.2lfi) + (%.2lf + %.2lfi) = %.2lf + %.2lfi\n",
           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) - (z1.ImagPart * z2.ImagPart);
    z3.ImagPart = (z1.RealPart * z2.ImagPart) + (z1.ImagPart * z2.RealPart);
    return z3;
}

Key takeaways to remember #

• Struct variables are declared like regular variables (Complex num;), not pointers unless you specifically need dynamic memory allocation.
• Always capture return values from functions that return data — calling read_complex() without assigning it to a variable means you lose the input value entirely.
• Use strcmp() for string comparisons to avoid fragile, bug-prone checks on individual characters.

内容的提问来源于stack exchange，提问作者printingwrong3434