isLetter function

bool isLetter(
  1. String character
)

Checks whether the given character is a letter.

This function takes a String representing a single character and returns true if the character is a letter (uppercase or lowercase), and false otherwise.

Implementation

bool isLetter(final String character) {
  // use this trick to see if the character can have different casing
  return character.toLowerCase() != character.toUpperCase();
}