Thread: Tiny thing in a simple parser - C++

Originally Posted by HelpMeC

At the end of such method - do I have to delete manually the smallerOne variable before the return?

Yes, you do. I would delete as soon as it is no longer used.

Originally Posted by HelpMeC

I thought that at the end of the method - everything is destroyed, including instances of the related class.
Am I wrong?

All non-static local variables would be destroyed, and that includes class instances. But again, what you have here is an ordinary pointer that is the non-static local variable. So, the pointer will be destroyed, but not what it points to, unless you manually do that yourself.

This is why we use smart pointers like std::unique_ptr instead: when the unique_ptr is destroyed because it falls out of scope, what it points to is also destroyed, so we don't have to manually destroy it.

Originally Posted by HelpMeC

What did you mean by this extra words: "and that includes class instances"? Can you maybe give an example to emphasize what that means?

See:

Code:

#include <iostream>
#include <string>

int main()
{
    std::string s{"hello world!"};
    std::cout << s << std::endl;
    // no need to clean up s here
}

Contrast with:

Code:

#include <iostream>
#include <string>
 
int main()
{
    auto p = new std::string{"hello world!"};
    std::cout << *p << std::endl;
    delete p;
}

Originally Posted by HelpMeC

Some memory has been allocated for that at all? I guess no, it's only a declaration...

It depends on context. If you're talking about the declaration of a local variable, then that declaration is a definition, so indeed memory has been allocated for it.

Originally Posted by HelpMeC

BTW, why the compiler warns about declaring const like that:

Post the smallest and simplest program that you expect to compile without any warnings, but which demonstrates this warning. Also, post the exact warning message corresponding to this simplified program.

Originally Posted by HelpMeC

Declaration - right, it has its required memory allocated in compile-time.

The memory allocation happens at run time, of course, but the compiler determines the amount of memory to be allocated for the size of the object at compile time, and then when the object is actually created, the constructor may arrange for the further dynamic allocation of memory.

Originally Posted by HelpMeC

BTW, if I want to consider lines starting with some white-space as invalid input. Can I change something elegantly at the final version of the parser, or should I have to add a condition in the beginning: if the first char of the line is a whitespace -> invalid input?

Well, the solution would be really simple with regex...

I'd just check the first char. It's simple enough once you know the string is not empty.

Here's another thing though: do you want to allow whitespace before and/or after the comma? As john.c pointed out, that's currently allowed.