2.1. First, there was struct

2.1. First, there was struct
	Chapter 2. Top of the class

2.1. First, there was `struct`

[ fromfile: classes.xml id: structs ]

In the C language, there is the struct keyword, for defining a structured chunk of memory.

Example 2.1. src/structdemo/demostruct.h

[ . . . . ]
struct Fraction {
    int numer, denom;
    string description;
};
[ . . . . ]

Example 2.1 shows the definition of a structured piece of memory, comprised of smaller chunks of memory. Each smaller chunk (numer, denom, description) is accessible by name.

Example 2.2. src/structdemo/demostruct.cpp

[ . . . . ]
void printFraction(Fraction f) { 
    cout << f.numer << "/" << f.denom << endl;
    cout << "  =? " << f.description << endl; 
}


int main() {
    
    Fraction f1;

    f1.numer = 4;
    f1.denom = 5;
    f1.description = "four fifths";
    
    Fraction f2 = {2, 3, "two thirds"}; 
    
    f1.numer = f1.numer + 2;
    printFraction(f1);
    printFraction(f2);
    return 0;
}
Output:

  6/5
  =? four fifths
  2/3  
  =? two thirds

	Passing a struct by value could be expensive if it has large components
	Member Initialization

Example 2.2 shows how we can use a structured chunk of memory (containing subobjects) as a single entity.