Convert String to Uppercase in Go

Strings are a built-in data type that represents sequences of characters in Golang. They are defined using double quotes (") and can contain any valid Unicode characters. In this article we will write a go language program to convert a string to uppercase. Here we will see the usage of both for loop and library functions to carry on the respective conversion.

Method, 1: Using user-defined function

In this method, we are going to create a user-defined function to convert a string into upper-case. The Steps to perform that are explained below ?

Algorithm

• Step 1 ? First, we need to import the fmt package.

• Step 2 ? Then, create a function to convert a string to uppercase. The function accepts the string as the argument. Convert the string obtained into byte variable and use a for loop to iterate over the byte.

• Step 3 ? Now, if the characters forming the string are in lowercase then take that particular character of the byte and subtract from it the difference between a and A which turns out to be 32.

• Step 4 ? After that subtract the difference from the values of the byte array and store them back to the byte array.

• Step 5 ? Return the byte array. start the main() function. Inside the main() initialize a string and print it on the screen.

• Step 6 ? Now call the ToUpper() function and pass the string as argument to it. store the result obtained in a variable called result and print the result on the screen.

Example

In this example, we will write a go language program to convert a string to uppercase by using an external function.

package main
import (
   "fmt"
)

//function to convert characters to upper case
func ToUpper(s string) string {
   b := []byte(s)
   for i, c := range b {
      if c >= 'a' && c <= 'z' {
         b[i] = c - ('a' - 'A')
      }
   }
   return string(b)
}

func main() {
   var input string = "convert this string to uppercase"
   fmt.Println("The given string is:\n", input)
   var output string = ToUpper(input)
   fmt.Println()
   fmt.Println("String obtained by converting the above string to uppercase is:\n", output)
}

Output

The given string is:
 convert this string to uppercase

String obtained by converting the above string to uppercase is:
 CONVERT THIS STRING TO UPPERCASE

Method 2: Using internal functions

In this method, we are going to use the internal function of golang to convert a normal string to upper-case string. The syntax used in this method are explained below ?

Syntax

func ToUpper(r rune) rune

ToUpper() function present in unicode package is used to convert a given string to uppercase. It takes the rune character as an argument and returns a rune in uppercase by converting the given rune to uppercase.

func ToUpper(str string) string

ToUpper() function is present in strings package and is used to convert a given string to uppercase. The function accepts the given string as argument and returns the final string after converting it to upper case.

func ToTitle(str string) string

ToTitle() function is present in strings package and is used to convert a string to uppercase. The function takes string to be converted as an argument to it and returns the string after converting its case to upper.

Algorithm

• Step 1 ? First, we need to import the fmt and Unicode package.

• Step 2 ? Now, create the toUpper() function that accepts the string whose case is to be changed and returns the string. Inside the function we are first converting the string obtained into rune and then using for loop to iterate over the rune array.

• Step 3 ? If the character of the array turns out to be in lowercase then we need to convert it to upper case by using Unicode.Upper() function by passing that character as argument to it.

• Step 4 ? Now, store the character one by one in the initialized array and return the final array.

• Step 5 ? Now, start the main() function. Here initialize a variable of type string and store value to it. further print the array on the screen.

• Step 6 ? Call the ToUpper() function by passing the string as argument to it and store the result in a variable and print it on the screen.

Example 1

In this example we will the Unicode package to convert a given string to uppercase in go programming language. In this function we will use the characters of the string one by one to convert them to uppercase.

package main
import (
   "fmt"
   "unicode"
)

func ToUpper(s string) string {
   a := []rune(s)
   for i, c := range a {
      if unicode.IsLower(c) {
         a[i] = unicode.ToUpper(c)
      }
   }
   return string(a)
}

func main() {
   var input string = "convert this string to uppercase"
   fmt.Println("The given string is:\n", input)
   var output string = ToUpper(input)
   fmt.Println()
   fmt.Println("The string obtained by converting above string to uppercase is:\n", output)
}

Output

The given string is:
 convert this string to uppercase

The string obtained by converting above string to uppercase is:
 CONVERT THIS STRING TO UPPERCASE

Example 2

In this example we will write a go language program to convert a string to uppercase by using the ToUpper() function present in strings package.

package main
import (
   "fmt"
   "strings"
)

func main() {
   var input string = "convert this string to uppercase"
   fmt.Println("The given string is:\n", input)
   var output string = strings.ToUpper(input)
   fmt.Println()
   fmt.Println("The string obtained by converting the given string to uppercase is:\n", output)
}

Output

The given string is:
 convert this string to uppercase

The string obtained by converting the given string to uppercase is:
 CONVERT THIS STRING TO UPPERCASE

Example 3

In this example we will use a go language program to convert a string to uppercase by using ToTitle() function.

package main
import (
   "fmt"
   "strings"
)

func main() {
   var str string = "This is a string to be converted"
   fmt.Println("The given string is:\n", str)
   fmt.Println()
   var res string = strings.ToTitle(str)
   fmt.Println("The string obtained by converting the above string to uppercase is:\n", res)
}

Output

The given string is:
 This is a string to be converted

The string obtained by converting the above string to uppercase is:
 THIS IS A STRING TO BE CONVERTED

Conclusion

We have successfully compiled and executed a go language program to convert a string to uppercase along with examples.