Pointers

 Pointers 

In computer programming, a pointer is a variable that stores the memory address of another variable. Pointers are used to store the addresses of other variables, which can be used to access and manipulate the value stored in the other variables.

They are a powerful tool that can be used to improve the efficiency of a program, but they can also be difficult to use correctly and can lead to bugs if not handled carefully.

Pointers can be used to pass variables by reference to functions, allowing the function to modify the value of the variable. They can also be used to dynamically allocate memory at runtime, which can be useful for creating data structures like linked lists and trees.

Pointers are used in computer programming for several reasons:

Efficiency: Pointers allow you to directly manipulate the memory location of a variable, rather than copying the value of the variable to a new location. This can be more efficient in terms of time and memory usage.

Dynamic memory allocation: Pointers can be used to dynamically allocate memory at runtime, which is useful for creating data structures like linked lists and trees.

Function parameters: Pointers can be used to pass variables by reference to functions, allowing the function to modify the value of the variable. This is useful when you want to modify a variable in a function and have those changes reflected in the calling function.

Array indexing: Pointers can be used to access array elements more efficiently. In C, for example, an array can be accessed using the [] operator, but this requires the compiler to perform additional calculations to determine the memory location of the element. Using a pointer, you can access array elements directly by incrementing the pointer.

Improved readability: Pointers can make code more readable by providing explicit references to memory locations. This can be especially useful when working with complex data structures like linked lists and trees.

Pointers in Go

In Go, pointers are variables that store the memory address of another variable. 

They are denoted by the * operator, which is used both to declare a pointer variable and to access the value stored at the address pointed to by the pointer.

Here is an example of how pointers are used :

In this example, p is a pointer to an int. The & operator is used to get the address of the variable x, and this address is stored in p. The * operator is used to access the value stored at the address stored in p, which is the value of x.

Pointers are used in Go for similar reasons as in other languages, such as to improve efficiency, pass variables by reference to functions, and to dynamically allocate memory. However, Go has a garbage collector that automatically reclaims memory that is no longer in use, so pointers are not as commonly used in Go as in languages like C and C++.

Here is an example of how you can use a pointer to modify the values of an array in Go:

This is an example of how pointers can be used to pass variables by reference in Go.

In this example, the modifyArray function takes a pointer to an array of 3 integers as an argument and modifies the values of the array elements. The main function declares an array of 3 integers and initializes it with the values 1, 2, and 3. It then calls the modifyArray function and passes the address of the array using the & operator.

When the modifyArray function is called, it modifies the values of the array elements and the modified array is printed by the main function. The output of the program is:

Original array: [1 2 3]

Modified array: [100 200 300]

Using a pointer in this way allows the modifyArray function to modify the values of the array in the calling function, rather than just returning a modified array.

Pointers can also be used with structs in Go to allow you to modify the values of struct fields in another function. Here is an example of how this can be done:

In this example, the Point struct has two fields, X and Y, which are both integers. The modifyPoint function takes a pointer to a Point as an argument and modifies the values of the X and Y fields. The main function declares a Point variable and initializes it with the values 1 and 2 for the X and Y fields, respectively. It then calls the modifyPoint function and passes the address of the Point variable using the & operator.

When the modifyPoint function is called, it modifies the values of the X and Y fields and the modified Point is printed by the main function. The output of the program is:

Using a pointer in this way allows the modifyPoint function to modify the values of the Point struct in the calling function, rather than just returning a modified struct. This is an also example of how pointers can be used to pass variables by reference in Go.

Pointers are used in Go for several reasons, such as:

To pass variables by reference: Pointers can be used to pass variables to functions, allowing the function to modify the value of the variable in the calling function. This is useful when you want to modify a variable in a function and have those changes reflected in the calling function.

Pointers are not commonly used in Go for several reasons:

Go has a garbage collector that automatically reclaims memory that is no longer in use, so it's not necessary to manually manage memory using pointers. This simplifies the process of memory management and reduces the likelihood of errors related to memory management.

Go has several built-in types and mechanisms for passing variables by reference, such as slices and maps, which are easier to use and less error-prone than pointers.

Pointers can make code more complex and harder to read, especially for inexperienced programmers. Go emphasizes simplicity and readability, and using pointers can sometimes work against these goals.

Go has a philosophy of "zero-cost abstractions", which means that the use of high-level abstractions should not come at the cost of performance. Pointers can sometimes have a negative impact on performance, and Go aims to minimize this impact as much as possible.

Overall, Go provides several alternatives to pointers that are more appropriate in most cases. While pointers can still be useful in certain situations, it's important to use them with caution and only when they are necessary.

Interview questions:

1. What is pointer with example

2. Que: function which takes array as param and change its value in another function using pointer