Problem Statement

Idiomatically determine all the lowercase and uppercase letters   (of the Latin [English] alphabet)   being used currently by a computer programming language. The method should find the letters regardless of the hardware architecture that is being used (ASCII, EBCDIC, or other).

Display the set of all: that can be used (allowed) by the computer program, where   letter   is a member of the Latin (English) alphabet:     a ──► z     and     A ──► Z.

You may want to mention what hardware architecture is being used, and if applicable, the operating system.

Let's start with the solution:

fn main() {
    println!(
        "Lowercase letters: {}",
        (b'a'..=b'z').map(|c| c as char).collect::<String>()
    );
    println!(
        "Uppercase letters: {}",
        (b'A'..=b'Z').map(|c| c as char).collect::<String>()
    );
}