just a random question

This is a discussion on just a random question within the C++ Programming forums, part of the General Programming Boards category; if it returns nothing then what would this result in, 0 or space? Code: #include <iostream> void test() { return; ...

  1. #16
    Registered User bobknows's Avatar
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    if it returns nothing then what would this result in, 0 or space?
    Code:
    #include <iostream>
    void test()
    {
           return;
    }
    
    int main()
    {
         cout << test();
    }

  2. #17
    Registered User bobknows's Avatar
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    also, what happens when you do this with while or if?
    Code:
    while/*or if*/(1; 0+1; /* and so on */ )
    {}

  3. #18
    C++まいる!Cをこわせ! Elysia's Avatar
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    Or how about a compile error?
    The second is a syntax error.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  4. #19
    Registered User bobknows's Avatar
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    probably, maybe i will try it

  5. #20
    C++まいる!Cをこわせ! Elysia's Avatar
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    Heh. Not probably. There will be a compile error. In two places, actually.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  6. #21
    Registered User bobknows's Avatar
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    you're right, i just tried it

  7. #22
    C++ Junkie Mozza314's Avatar
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    Quote Originally Posted by Elysia View Post
    return; does not return void, though. It returns nothing.
    Sounds like hair splitting to me; "void" means "nothing" right? Is there a technical difference?

  8. #23
    C++まいる!Cをこわせ! Elysia's Avatar
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    Yes, because void is treated as a type.
    Try, for example:

    Code:
    void foo() {}
    int main() { int x = foo(); }
    error C2440: 'initializing' : cannot convert from 'void' to 'int'.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  9. #24
    Registered User whiteflags's Avatar
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    void doesn't even have a size, so it is nothing. I don't see a meaningful difference here. It is equally erroneous to state that just because a function has no value to return, that it will never return because "you cannot return void". The only circumstance any function does not return would be because it does not reach an exit point. Compilers do complain about unreachable code in a couple of ways.

    Code:
    void foo() {}
    int main() { int x = foo(); }
    Blatant mistakes don't really prove your point. This is the same error as any invalid type conversion.

  10. #25
    C++まいる!Cをこわせ! Elysia's Avatar
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    My point is that the compiler treats it as something. While in your return statement you don't put void to return nothing, you simply leave it empty.
    It is my understanding or interpretation of the whole anyway. "void" can be seen as a type.
    (Otherwise why would void* be legal? And why not void in the parameter list be legal?)
    Void is a curious thing, yet there. Semantics.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  11. #26
    Registered User whiteflags's Avatar
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    My point is that the compiler treats it as something. While in your return statement you don't put void to return nothing, you simply leave it empty.
    I would think the inverse -- if the compiler treated void as something, then you would need to create it to appease the compiler. You don't need to do that, and thank goodness, because you can't. Meanwhile void* is something, because it's a data pointer. Symmetry is for the deluded people.

    I'm not saying void isn't a type, but saying it is nothing would be perfectly correct. After all, returning void means returning nothing. In common vernacular it's just harmless.

  12. #27
    C++まいる!Cをこわせ! Elysia's Avatar
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    Meh. Whatever.
    void is special; let's just be content with that.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  13. #28
    Registered User bobknows's Avatar
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    thats a good way to put it,
    why would you have main return anything other than 0 though?

  14. #29
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    Quote Originally Posted by bobknows View Post
    thats a good way to put it,
    why would you have main return anything other than 0 though?
    To let the caller know how the execution went. Let's say you wrote a program that just output the contents of a file to the console. On success, your program would return 0. If your program failed to open the specified file then main() could return 1, letting the caller know that something went wrong.
    If you understand what you're doing, you're not learning anything.

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