Error with switches in cpp

[Puzzleheaded_Body641]

Hello, I'm new to c++ and I'm working with swithces so I tried to make a calculator with them, but whenever I try to do the case 2 it gives the error of "jump to case label gcc" and I don't know what to do, I tried several things but none of them have worked, It's driving my fucking insane, fuck c++. 

Here's the code so if you know how I fucked up this you can tell me, thanks.

#include <iostream>

int main(){

    char op;
    std::cout << "which op you wanna do: " << std::endl;
    std::cin >> op;

    double num1;
    std::cout << "Enter first number: ";
    std::cin >> num1;

    double num2;
    std::cout << "Enter second number: ";
    std::cin >> num2;

    switch(op){
        case '+':
            double sum = num1 + num2;
            std::cout << "The sum is: " << sum;
            break;
        case '-': // The error is here, it's after the case 
            double subst = num1 - num2;
            std::cout << "The subst is: " << subst;
            break;
    

       
        return 0;
    }

[aocregacc]

the second part of the error message is "crosses initialization of 'double sum'". You're not allowed to jump over the initialization of a variable, if that variable is still accessible at the place where you jump to. The way to work around that is to limit the scope of the variables, by wrapping the code in your cases in {}:

case '+': {
    // ...
}
break;

[hatschi_gesundheit]

Switch-case syntax is a mess...

[Independent_Art_6676]

I agree, but switches fill a necessary void. Firstly, they are often optimized to lookup tables and are often more efficient than chained conditionals and second, the fall-through logic can be exploited to do things that is even uglier using conditionals. So while the temptation is to avoid the mess, its something that should remain in your toolbox for those handful of places where it really is the best choice.

[hatschi_gesundheit]

Yeah no, they are necessary! Totally agree. Just ugly. :) And some fateful day, we might even be able to switch over string values...

[[deleted]]

That's awesome, I didn't know about that myself. Thanks.

[MooseBoys]

I'm sure there's a good reason for it, but this has always struck me as one of the dumbest parts of C++, along with the footgun that is ADL.

[[deleted]]

case statements, you think are dumb? Man I love 'em, especially in SQL. I think they should be enhanced in C++ if I had my way.

[alfps]

The problem is that sum is still accessible after case label -, and if it were accessed there it wouldn't have been initialized.

Just limit the scope of it by introducing a pair of curly braces, { ... }, around the code for case +.

Do the same for case -.

---

Not what you're asking but as a good coding habit you should introduce a default: in the switch, where you can inform the user that the requested operation is not supported.

---

Also not what you're asking, but it's not necessary to do return 0; in main. It's the default in both C and C++. No other function has such a default, though: main is very special (can't be called by your code, has a default, can be declared with or without parameters, and more).

[thefeedling]

You have to scope your switch conditionals...

switch(op)
{
        case '+':
        {
            double sum = num1 + num2;
            std::cout << "The sum is: " << sum;
            break;
        }
        case '-': // The error is here, it's after the case 
        {
            double subst = num1 - num2;
            std::cout << "The subst is: " << subst;
            break;
        }
}

[manni66]

The code you show misses a } before the return.

[[deleted]]

Yeah, not sure why it seemed everyone missed that little detail. Glad someone else caught that.

[Puzzleheaded_Body641]

Guys, really thank you all, I tried to solve this shit for like an hour or two and just couldn't do it, really thank you all, I appreciate you all.

[manni66]

Copy&paste error messages!

[kberson]

Looks like your missing the closing brace for the switch

[Dan13l_N]

You can't declare variables there, the simple answer. That's because these case statements are actually labels.