import Foundation
// Define possible errors for validation
enum ReplaceDigitError: Error {
case invalidDigit
case positionOutOfRange
case nonDigitCharacter
}
// Function to replace a digit at a given position in a floating-point number
func replaceFloatDigit(number: Double, position: Int, newDigit: Character) throws -> Double {
// Validate that newDigit is indeed a single digit
guard newDigit.isNumber else {
throw ReplaceDigitError.invalidDigit
}
// Convert number to string with fixed precision (10 decimal places)
let strNum = String(format: "%.10f", number)
// Validate position
guard position >= 0 && position < strNum.count else {
throw ReplaceDigitError.positionOutOfRange
}
// Ensure position points to a digit
let index = strNum.index(strNum.startIndex, offsetBy: position)
let ch = strNum[index]
if ch == "." || ch == "-" {
throw ReplaceDigitError.nonDigitCharacter
}
// Replace digit (strings are immutable, so build a new one)
var chars = Array(strNum)
chars[position] = newDigit
let modified = String(chars)
// Convert back to Double
guard let result = Double(modified) else {
throw ReplaceDigitError.invalidDigit
}
return result
}
// Main function
func main() {
do {
let num = 89710.291
let pos = 2 // 0-based index
let newDigit: Character = "8"
let result = try replaceFloatDigit(number: num, position: pos, newDigit: newDigit)
// Print result with 3 decimal places
print(String(format: "Modified number: %.3f", result))
} catch {
print("Error: \(error)")
}
}
main()
/*
run:
Modified number: 89810.291
*/
