How to convert an ASCII character to uppercase in Rust

Overview

ASCII stands for American Standard Code for Information Interchange. It is a way of encoding a character set used for communication between computers. ASCII is the first among many encodings such as the UTF-8, ISO-8859-1, and so on.

A character is an ASCII character if it is a number between 0 and 9, an uppercase or lowercase letter from the English alphabet, or some special character. In Rust, we can use the is_ascii() method to check if a character is within the ASCII range.

Rust provides two methods to convert an ASCII lowercase character to uppercase: to_ascii_uppercase() and make_ascii_uppercase().

Note: These methods have no effect on characters that are ASCII numbers, ASCII special characters, and non-ASCII characters.

Syntax

The code snippet below demonstrates how to use the to_ascii_uppercase() method.

character.to_ascii_uppercase()

The following code snippet demonstrates how to use the make_ascii_uppercase() method.

character.make_ascii_uppercase()

Parameters

Both methods require one input parameter:

  • character: This is the character we want to convert to uppercase.

Return value

The to_ascii_uppercase() method returns the uppercase ASCII equivalent of the input character. The above code snippet for to_ascii_uppercase() will return the uppercase equivalent for character.

The make_ascii_uppercase() method converts the input character to its uppercase ASCII equivalent. The above code snippet for make_ascii_uppercase() will convert the character to its uppercase equivalent.

Example

Let’s look at a few examples that use the above two methods to convert characters to uppercase in Rust.

fn main(){
  // Create characters
  let char1 = 't';
  let char2 = '❤';
  let char3 = '!';
  // use to_ascii_uppercase() to convert to uppercase
  println!("{} uppercase is {}", char1, char1.to_ascii_uppercase());
  println!("{} uppercase is {}", char2, char2.to_ascii_uppercase());
  println!("{} uppercase is {}", char3, char3.to_ascii_uppercase());
  // Create characters
  let mut char4 = 'a';
  let mut char5 = '❤';
  let mut char6 = '!';
  // use make_ascii_uppercase() to convert to uppercase
  char4.make_ascii_uppercase();
  char5.make_ascii_uppercase();
  char6.make_ascii_uppercase();
  // print uppercase characters
  println!("{}", char4);
  println!("{}", char5);
  println!("{}", char6);
}

Explanation

  • Lines 1–3: We create three characters. Only the first character, char1, is an ASCII letter character.
  • Lines 7–9: We use to_ascii_uppercase() to convert the above three characters to uppercase and print the result. The output shows that to_ascii_uppercase only returns a different value for char1.
  • Lines 11–13: We create three more characters. Only char4 is an ASCII letter character.
  • Lines 15–17: We use make_ascii_uppercase() to convert the new characters to uppercase.
  • Lines 19–21: We print char4, char5, and char6. The output shows that make_ascii_uppercase only changed the value of char4.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)