09_errors.cml

// A function that may fail returns T!; `throw` returns an error value.
// Run: camel docs/tutorial/examples/09_errors.cml
module errors

func safe_div(a: int, b: int): int! {
    return if b == 0 then {
        throw error('DivByZero', 'the divisor is zero')
    } else {
        return a / b
    }
}

func inc(x: int): int { return x + 1 }

func describe(r: int!): string {
    return match r {
        case error e => e.kind + ': ' + e.message
        case v => 'ok ' + string(v)
    }
}

func main(): int sync {
    println(safe_div(9, 3) !! -1)            // 3
    println(safe_div(9, 0) !! -1)            // -1: the substitute
    println(describe(safe_div(8, 2) ?-> inc))
    println(describe(safe_div(8, 0) ?-> inc))
    println(parse_int('12') !! 0, parse_int('twelve') !! 0)
    println(safe_div(1, 0))
    return 0
}