carbon language

Carbon is still under development and lacks certain features like for loops and comparison operators like <. However, we can still achieve the Fibonacci sequence using other techniques. Here’s one approach:

fn Main() -> i32 {
  let mut number: i32 = -1
  let mut previousNumber: i32 = 1

  // Prompt user for input
  Print("Enter a positive integer: ")
  let input = ReadLine()

  // Convert input to i32
  let n = Try(input.Trim().Parse())

  // Handle potential parsing errors
  if n.IsError() {
    Print("Invalid input. Please enter a positive integer.")
    return 1
  }

  // Iterate n times with custom loop logic
  while n.Value() > 0 {
    // Calculate next number and update previous
    let nextNumber = number + previousNumber
    previousNumber = number
    number = nextNumber

    // Decrease iteration counter
    n.Value() -= 1
  }

  // Print the result
  Print("The nth Fibonacci number is {0}", number)
  return 0
}

Explanation:

  • We initialize two variables, number and previousNumber, to hold the current and previous Fibonacci numbers.
  • We prompt the user for an integer and read the input with ReadLine().
  • We use Try and IsError to safely convert the input to an i32 and handle potential parsing errors.
  • Since loops and comparisons are not yet available, we use a custom loop structure with while and decrementing the n value each iteration.
  • Inside the loop, we calculate the next Fibonacci number (sum of previous two) and update the previous number.
  • Finally, we print the nth Fibonacci number stored in number.

This implementation uses an iterative approach instead of recursion due to Carbon’s current limitations. It demonstrates how to achieve the desired functionality despite the language’s ongoing development.