about constructor and class

Hi guys,

I wanted to know that if we are making a program eg.for music items.

Can we write the class as:

Code:

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class Music_item

{

private:

int song;

public:

Music_item(); ----> default constructor


};

---

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Will their be any problem if we write the class and its constructor with an underscore?

that appears to be valid code. without knowing your requirements, it's hard to know if will be adequate to do what you want it to do.

If your constructor has no user defined code is there any requirement for it? As far as i recall I I have always written a declaration as a matter of course, but i understood that c++ would just initialise everything to binary 0 if no constructor was typed by the coder. As a backward compatability step with C code constructs, Does that still apply in the new standard?

Quote:

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Originally Posted by rogster001

As far as i recall I I have always written a declaration as a matter of course, but i understood that c++ would just initialise everything to binary 0 if no constructor was typed by the coder. As a backward compatability step with C code constructs, Does that still apply in the new standard?

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That was never the case, even before C++11. If your class contains members of built-in types or PODs, they won't get initialized to anything unless you make it so by supplying a user-defined constructor in which you explicitly initialize those members.

Quote:

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Will their be any problem if we write the class and its constructor with an underscore?

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The only time you would ever have a problem with an underscore in a variable, function name would be if it was a leading underscore. Many of the standard library functions use underscores. See this documentation for std::string and you should notice functions such as c_str(), etc.


Jim

Quote:

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Originally Posted by jimblumberg

The only time you would ever have a problem with an underscore in a variable, function name would be if it was a leading underscore. Many of the standard library functions use underscores. See this documentation for std::string and you should notice functions such as c_str(), etc.


Jim

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The standard reserves GLOBAL identifiers with a LEADING underscore for use by compiler vendors. All identifiers with 2 consecutive underscores are also reserved. A single underscore in the middle of an identifier is never a problem.

EDIT: I just reread your post and realized that you never actually implied anything to the effect of the boldened part. Sorry, reading comprehension fail on my part.

Quote:

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The standard reserves GLOBAL identifiers with a LEADING underscore for use by compiler vendors.

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This is true, but in practice you need to avoid defining any labels with a leading underscore.

You see, a lot of standard library implementations interpreted that in such a way that it allowed macros at global scope of that form to be reserved.

In other words, a lot of standard library implementations define macros which don't honor scope so the notion that you can use labels of that form in a smaller scope is flawed.

Soma

Quote:

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The standard reserves GLOBAL identifiers with a LEADING underscore for use by compiler vendors. All identifiers with 2 consecutive underscores are also reserved. A single underscore in the middle of an identifier is never a problem.

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And you're telling me this for? As I said the only time you would ever have a problem is when you use a leading underscore. I didn't say when because it doesn't really matter in this context. In my opinion you should avoid using a leading underscore for any variable, I don't care where you use it I consider using a leading underscore a bad practice.


Jim

Quote:

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Originally Posted by jimblumberg

And you're telling me this for?

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Read my edit.

Quote:

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Originally Posted by antred

That was never the case, even before C++11. If your class contains members of built-in types or PODs, they won't get initialized to anything unless you make it so by supplying a user-defined constructor in which you explicitly initialize those members.

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Ok so forget the initialisation, although that has been written in published books - no guarantee i know, but regardless, I mean the fact you can / could instansiate an object without writing a constructor declaration in the class declaration

Quote:

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could instansiate an object without writing a constructor declaration in the class declaration

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This still holds; if you don't write a default constructor the compiler will provide one.

Soma

Quote:

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Originally Posted by phantomotap

This still holds; if you don't write a default constructor the compiler will provide one.

Soma

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Exactly - like a solictor in a legal case...!

O_o

Did you ask that just to setup a really bad joke?

Soma