// for i, v in arr — iterate with both index and value

fn main() {
    let fruits = ["apple", "banana", "cherry"]
    
    // basic indexed iteration
    for i, v in fruits {
        println("${i}: ${v}")
    }
    
    // use the index for computation
    let nums = [10, 20, 30, 40, 50]
    mut sum = 0
    for i, v in nums {
        if i % 2 == 0 {
            sum += v
        }
    }
    println("sum of even-indexed elements: ${sum}")
    
    // build a new array using index
    let letters = ["a", "b", "c", "d"]
    let tagged = []
    for i, v in letters {
        push(tagged, "${v}${i}")
    }
    println(tagged)
    
    // plain for-in still works (no index)
    for v in fruits {
        print(v)
        print(" ")
    }
    println("")
}