// string interpolation: embed expressions inside "..." with ${}

fn main() {
    let name = "alice"
    let age = 30
    
    // simple variable interpolation
    println("hello ${name}!")
    
    // multiple interpolations
    println("${name} is ${age} years old")
    
    // expression inside interpolation
    println("${name} will be ${age + 1} next year")
    
    // interpolation with function calls
    let nums = [10, 20, 30]
    println("first element: ${nums[0]}")
    
    // string concatenation with interpolation
    let greeting = "hi"
    println("${greeting}, ${name}! age=${age}")
    
    // no interpolation (regular string)
    println("no interpolation here")
    
    // empty interpolation adjacent to text
    let x = 42
    println("value is ${x}")
    
    // arithmetic in interpolation
    println("double age: ${age * 2}")
}