Struct errors with C++?

Question

so I am reading C++primer 6th edition and am up to structs, but when trying to make a test file to run I get the following error:

xubuntu@xubuntu:~/C/C$ make test
g++     test.cpp   -o test
test.cpp: In function ‘int main()’:
test.cpp:14:41: error: expected primary-expression before ‘.’ token
make: *** [test] Error 1
xubuntu@xubuntu:~/C/C$

The code:

#include <iostream>
#include <stdio.h>

struct test{
        char name[20];
        float age;
        float worth;
};

int main(){
        using namespace std;
        test chris = {"Chris", 22, 22};
        cout << "This is Chris's data:" << test.chris;
        return 0;
}

Answer 1

You may try doing it like this:-

cout << "This is Chris's name:" << chris.name;

test is the name of the struct and chris is the variable name.

Answer 2

test is the name of the struct, chris is the name of the variable, so you need to be referring to chris . And you'll need to reference each field individually to print it out. IE:

cout << "This is Chris's name:" << chris.name;
cout << "This is Chris's age:" << chris.age;

Answer 3

cout << "This is Chris's data:" << test.chris this is wrong.

It should be cout << "This is Chris's data:" << chris.name

Answer 4

The answer is clearly written : test.cpp:14:41: error: expected primary-expression before '.' token

replace

cout << "This is Chris's data:" << test.chris;

with

    cout << "This is Chris's data:" << chris.name << " " << chris.age;

Answer 5

You're calling test.chris .

chris is the name of your struct variable.

What you want to call is chris.name .

Answer 6

That's because test.chris doesn't exist.

You want to use the chris.name , chris.worth , chris.age directly.

If you want to use something like std::cout << chris you have to overload the << operator. For example:

std::ostream& operator<<(std::ostream &stream, const test &theTest) {
     stream << "Name: " << theTest.name << ", Worth: " << theTest.worth << ", Age: " << theTest.age;
     return stream;
}

Then you could use it like this:

    test chris = {"Chris", 22, 22};
    cout << "This is Chris's data:" << chris;

Answer 7

Since no one has yet mentioned it, if you still want to use

cout << "This is Chris's data:" << // TODO

consider overloading the output stream operator "<<". This will tell the compiler what to do when it encounters a test object as the right-operand of the output stream operator.

struct test{
    char name[20];
    float age;
    float worth;
};

ostream & operator<<(ostream &, const test &);       // prototype

ostream & operator<<(ostream & out, const test & t){ // implementation
    // Format the output however you like
    out << " " << t.name << " " << t.age << " " << t.worth;
    return out;
}

so that this line now works:

cout << "This is Chris's data:" << chris;

Answer 8

test.chris does not exist. If you want to output the whole struct, you need to do something like:

std::cout << "This is Chris's Data:  " << chris.name << ", " << chris.age << ", " << chris.worth << std::endl;