Thread: struct question

This is just invalid syntax because you forgot the terminating semi-colon:

Code:

typedef struct
{
    int a;
} struct_ex

It is good that you posted your code within code bbcode tags, but you also need to indent your code properl.

Originally Posted by amahmoo

I am confused on how to pass values to a object in a union within a struct?

Why do you want to do this?

I suggest that you do not use a union because you probably don't need it, hence your reluctance to answer my question.

Originally Posted by amahmoo

I need the union there i need to do this for my hw for school

Besides this being homework, why do you need the union?

Originally Posted by amahmoo

laserlight can you help?

No, because I cannot make head or tail what you are trying to do. You're basically dumping syntactically invalid code, or semantically suspect code, and then expecting that someone will figure it out for you.

Rather, you should start with an overview of what you are trying to do. What is the problem that you are writing code to solve?

Then, show the code. The code should be properly formatted, especially where indentation is concerned. It is usually a good idea to post the smallest and simplest (compilable) program that demonstrates the error, if not at least post a self-contained snippet, e.g., a function that does not rely on global variables and other declarations that are not shown.

Finally, explain how does your code not work. Is it a compile error? If so, what is the exact error message? Is it a logic error? If so, what is the test input, expected output, and actual output? Does your program crash? If so, run it through a debugger and pinpoint on which line did the crash happen: that can help narrow down where the mistake might be, and of course you would provide details about test input, etc.

Originally Posted by amahmoo

i am just trying to set a to 1 using the following code up there its from my hw he told us to do it this way it doesnt matter what you think is semantically correct he just doing it to think differently

What exactly did your instructor say? You're basically saying "my instructor told me to do this, but it doesn't work". When I ask you what you're trying to do, you reply "what my instructor told me". You might as well ask your instructor for help because no one else has the necessary information to help you. We could guess, but if you really did what your instructor told you and refuse to accept anything else, for all we know the mistake lies with your instructor.

By the way, are you programming in C or C++?

EDIT:

Originally Posted by amahmoo

it doesnt matter what you think is semantically correct he just doing it to think differently

If you're saying that what I think doesn't matter, why should I bother helping you? My thoughts don't matter, right? I'm not relevant, a non-entity. Go ask your instructor for help. You're paying him, not me.

Originally Posted by amahmoo

I am programming in c

Right. Did your instructor really tell you to do:

Code:

#include <iostream>
using namespace std;

We may have told you before, but that's a C++ header and the using directive is C++ syntax.

Originally Posted by amahmoo

look i didn't mean what you think doesn't matter. What you say does matter. I am sorry i didn't mean to sound that way also its my fault i am not clear in what i am asking is becase i dont understand what i am supposed to do.

Fair enough. Well, start by indenting your code properly:

Code:

#include <iostream>

using namespace std;

typedef struct
{
    int a;
} struct_ex;

typedef struct example_1
{
    union
    {
        struct_ex object_ex;
    } test1;
} ex_1;

int main()
{
    ex_1 ex_obj;
    struct_ex *z = &ex_obj->test1.object_ex;
    z->a = 1;
}

Now, it is easy to see that ex_obj is an ex_1 object. Therefore, it has a member named test1, which you should access as ex_obj.test1. ex_obj.test1 is a union with only one member, named object_ex. Therefore, you should access this member as ex_obj.test1.object_ex. So, if you want a pointer to this object:

Code:

struct_ex *z = &ex_obj.test1.object_ex;