What Is A Loop And Why We Need Loop In Programming

Loop help us in doing the repetitive task for example you have to clean your house daily now this is a repetitive task to solve the same we get a tool a cleaning machine to do the moping for us now we need loops to to all our repetitive task in the world of programming language.

Let’s Take A Deeper Look

For example you want to display table of 2 (2, 4, 6, 7 ..) now you are not going to write so many print statements to do te same we can use a loop and just write one print statement in that loop and it will do the task to print all the cities for us.

Loop
	<statement>

Result:

<statement>
<statement>
<statement>
<statement>
<statement>
<statement>
..........

For Loop In Go Lang

Go language support only one loop for. In for loop we have a few sections where we can initialize variables, apply conditions based on that loop will deicide weather it has to execute the body or not, write some expression to control the number of iterations by changing the condition of the loop and body where we write our statements.

Note: Using of () is not supported you are not supposed to use the same or you will get the error.

for <initialization step>; <condition>; <expression> {
	<body>
}

initialization step -> In This step we can assign or create a variable that can be used in the loop it’s not mandatory to pass the initialization step but don’t forget to add ; if you are not writing expression in the loop. If you are defining some variable in initialization step then it will not be visible outside the loop.

for i := 1 ; i <= 10; i = i +1 {  // Okay
for ; i <= 10; i = i +1 {		  // Okay
for i <= 10; i = i +1 {		      // Error

condition -> Here we write the condition based on the loop will deicide that weather it has to execute the body or not it’s not mandatory to pass the condition but you will end up in a infinite loop it can be stopped using break statement.

for i := 1 ; i <= 10 ; i = i +1 {		// Okay
for i := 1 ; ; i = i +1 {			    // Okay
for i := 1 ;  i = i +1 {		        // Error

expression -> Here we write some expression to change the value of variables that may change the condition after iteration and help in controlling the number of iterations it’s not mandatory to pass the expression but don’t forget to add ; if you are not writing expression in the loop.

for i := 1 ; i <= 10; i = i +1 {  // Okay
for i := 1 ; i <= 10; {			  // Okay
for i := 1 ; i <= 10 { 			  // Error

There is one more case where we are not defining any of the above statement again this will be an infinite loop.

for {
	<statement>
}

body -> In this section of the loop we actually wite the code we want to run repetitively writing the body is also not mandatory I know it’s useless but it is possible.

Using For Loop With Range

range keyword in go lang can pass a single value to the loop on every iteration till the end of the iterator. for example if you range over "vipin" using for loop it will give the value "v" on the first run then "i" on the second run then "p" on the next one and so on. Another use case is iterating using a integer.

NOTE: Iterating over an integer can be done using range only after go version 1.22 you can check the same via command go version.

Here is the syntax for the same

for <variable_name_for_element> := range <iterator> {
	<statement>
	<statement>
	<statement>
}

Example:

package main

import ("fmt")

func main(){

	for element := range 10 {

		fmt.Println(element)

	}

}

Output:

It always print 1 value less then the given value as it stats from 0.

Doc was written in this livestream [Learn Go Day 10] and [Learn Go Day 12]