use std::error::Error;
/// Replace a digit at a given position in a floating-point number.
fn replace_float_digit(number: f64, position: usize, new_digit: char) -> Result<f64, String> {
// Validate that new_digit is indeed a single digit
if !new_digit.is_ascii_digit() {
return Err("Replacement must be a digit (0-9).".to_string());
}
// Convert number to string with fixed precision (10 decimal places)
let str_num = format!("{:.10}", number);
// Validate position
if position >= str_num.len() {
return Err("Position is out of range for the number string.".to_string());
}
// Ensure position points to a digit
let ch = str_num.chars().nth(position).unwrap();
if ch == '.' || ch == '-' {
return Err("Position points to a non-digit character.".to_string());
}
// Replace digit
let mut chars: Vec<char> = str_num.chars().collect();
chars[position] = new_digit;
let modified: String = chars.into_iter().collect();
// Convert back to float
match modified.parse::<f64>() {
Ok(result) => Ok(result),
Err(_) => Err("Conversion failed.".to_string()),
}
}
fn main() -> Result<(), Box<dyn Error>> {
let num = 89710.291;
let pos = 2; // 0-based index
let new_digit = '8';
match replace_float_digit(num, pos, new_digit) {
Ok(result) => {
// Print result with 3 decimal places
println!("Modified number: {:.3}", result);
}
Err(e) => {
eprintln!("Error: {}", e);
}
}
Ok(())
}
/*
run:
Modified number: 89810.291
*/
