use std::f64;
/*
Returns the first digit of a floating‑point number.
Approach:
- Convert the number to a string using to_string().
- Trim whitespace.
- If the number is negative, skip the leading '-' sign.
- Read the first numeric character.
- Convert that character back into an integer.
This avoids math‑based digit counting, which can be unreliable with floats.
*/
fn get_first_digit(value: f64) -> u32 {
// Convert the number to a trimmed string representation
let text: String = value.to_string().trim().to_string();
// Handle negative numbers by skipping the leading '-'
let first_char: char = if text.starts_with('-') {
text.chars().nth(1).unwrap()
} else {
text.chars().nth(0).unwrap()
};
// Convert the character to a digit
first_char.to_digit(10).unwrap()
}
/*
Main program.
*/
fn main() {
let f: f64 = 376.287152;
let first_digit: u32 = get_first_digit(f);
println!("{}", first_digit);
}
/*
run:
3
*/
