How to check whether a character is in the Alphabet or not in Golang?

In this tutorial, we will learn how to check whether the character is an alphabet or not. This tutorial includes two ways to achieve this −

First, using the built-in function isLetter() present in the fmt library will reduce the line of codes.

Another way is to use the concept of ASCII values as every character has a unique ASCII value using which we can find out whether the current character is an alphabet or not.

The ranges of uppercase and lowercase alphabets are as follows −

uppercase alphabets – 65 to 90

lowercase alphabets – 97 to 122

If the ASCII value of the character lies between the above ranges then the character is an alphabet.

Method 1: Using isLetter(0 function

In this example, we will use the built-in function isLetter() present in the fmt library to check whether the character is an alphabet.

Syntax

The isLetter() present in fmt library syntax is below. This function accept a character as argument.

Func isLetter(r rune) bool

Algorithm

• Step 1 − Initialize the string of characters.

• Step 2 − Run a for loop over the string.

• Step 3 − Start an if condition and call IsLetter() function in the if condition.

• Step 4 − Print the result accordingly.

Example

package main
import (
   
   // fmt package provides the function to print anything
   "fmt"
   
   // unicode function is providing isLetter function
   "unicode"
)
func main() {
   // declaring and initializing the variable using the shorthand method in Golang
   characters := "A&j()K"
   fmt.Println("Golang program to check the character is an alphabet or not using IsLetter() function present in the Unicode library.")
   
   // running a for loop to check each character in the string is alphabet or not
   for i := 0; i < len(characters); i++ {
      
      // calling the Isletter() function and printing the result on the basis
      // of return value of the function
      if unicode.IsLetter(rune(characters[i])) {
      fmt.Printf("%c is a character.\n", characters[i])
      } else {
         fmt.Printf("%c is not a character.\n", characters[i])
      }
   }
}

Output

% go run tutorialpoint.go
Golang program to check whether the character is an alphabet or not using the IsLetter() function present in the Unicode library.
A is a character.
& is not a character.
j is a character.
( is not a character.
) is not a character.
K is a character.

Method 2:Using ASCII characters

In this example, we will use the ASCII characters range to check whether the character is an alphabet or not.

Syntax

The comparison will be make using the range of ASCII value of lower and uppercase alphabets as shown in below syntax.

if (characters[i] >= 65 && characters[i] <= 90) || (characters[i] >= 97 && characters[i] <= 122) { }

Algorithm

• Step 1 − Initialize the string of characters.

• Step 2 − Run a for loop over the string.

• Step 3 − Start an if condition and compare the ASCII value of the current index character if it lies between 65 and 90 or 97 and 122.

• Step 4 − Print the result accordingly.

Example

package main
import (

// fmt package provides the function to print anything
   "fmt"
)
func main() {

   // declaring and initializing the variable using the shorthand method in Golang 
   characters := "A&j()K"
   fmt.Println("Golang program to check whether the character is an alphabet or not using the concept of ASCII values.")
   
   // running a for loop to check if each character in the string is alphabet or not
   for i := 0; i < len(characters); i++ {
   
      // checking that the ASCII value of the character is in between the range
      // of uppercase or lowercase characters or not
      if (characters[i] >= 65 && characters[i] <= 90) || (characters[i] >= 97 && characters[i] <= 122) {
         fmt.Printf("%c is a character.\n", characters[i])
      } else {
         fmt.Printf("%c is not a character.\n", characters[i])
      }
   }
}

Output

% go run tutorialpoint.go
Golang program to check whether the character is an alphabet or not using the concept of ASCII values.
A is a character.
& is not a character.
j is a character.
( is not a character.
) is not a character.
K is a character.

Conclusion

These are the two ways to check whether the character is an alphabet or not. The first way is more suitable in terms of modularity and code reusability. To learn more about go you can explore these tutorials.