task_034_pointers

Pointers

This code demonstrates the concept of pointers in Go and how they can be used to modify the value of a variable indirectly via its memory address. Let's break it down step by step.

1. Pointers Introduction: A pointer is a variable that stores the memory address of another variable. In Go, the & operator is used to get the memory address of a variable, and the * operator is used to access the value stored at a particular address.

2. Main Function:

   x := 45
   fmt.Println("The value of x is ", x)
   fmt.Println("The address of x is ", &x)
   changeValue(&x)
   fmt.Println("The new value of x is ", x)

   • x := 45: Initializes an integer x with a value of 45.
   • &x: Returns the memory address where x is stored.
   • changeValue(&x): Passes the address of x to the changeValue function. This allows the function to modify the value of x indirectly.

3. changeValue Function:

   func changeValue(y *int) {
       fmt.Println("The address of y is " , y)
       fmt.Println("The value stored at that address is " , *y)
       *y = 49
       fmt.Println("The new value at y is " , *y)
   }

   • The function takes a pointer to an integer (*int) as its parameter. This means y is a pointer that can store the address of an integer.
   • y: Holds the address of the passed variable (in this case, the address of x).
   • *y: Dereferences the pointer, i.e., it accesses the value stored at the address that y is pointing to.
   • *y = 49: Changes the value stored at the address y is pointing to. Since y is pointing to x, this modifies the value of x.

4. Output:

   When the program is executed, you will see:

   • The initial value of x.
   • The memory address of x.
   • The memory address stored in y (which is the same as the address of x).
   • The value stored at that address (which is the initial value of x).
   • The new value at the address after the change.
   • The new value of x after the function call.

In essence, this program demonstrates how you can use pointers to pass the address of a variable to a function and change the variable's value through its memory address, allowing for indirect modification of variables in Go.

Output

$ go run main.go                              
The value of x is  45
The address of x is  0x140000140d0
The address of y is  0x140000140d0
The value stored at that address is  45
The new value at y is  49
The new value of x is  49