Finding the power of a number

[Ebin]

how to find power of number in rust language like 2-raise-32

[pcpthm]

You can use pow method of each number type to compute an integral power of an integer. e.g. 2³² can be computed by 2u64.pow(32). Note that i32 or u32 cannot represent 2³², So you have to use one of the bigger types.

A gotcha is you cannot write 2.pow(5) because the type of 2 is not determined (can be u32, u64 or other types). You have to specify number type by either using suffix like 2u32.pow(5) or specifying the type of a variable let x: u32 = 5; x.pow(5).

[nop_thread]

I don't understand what you mean (because I'm not good at English), but if you want log_2(32), then you can use u64::leading_zeros().

fn main() {
    let log2_32 = (64 - 1) - 32u64.leading_zeros();
    println!("log_2 32 = {}", log2_32); // => 5

    let log2_100 = (64 - 1) - 100u64.leading_zeros();
    println!("log_2 100 = {}", log2_100); // => 6
}

If you want to round up the result, use u64::next_power_of_two() and then use .leading_zeros().

fn main() {
    let log2_32 = (64 - 1) - 32u64.next_power_of_two().leading_zeros();
    println!("ceil(log_2 32) = {}", log2_32); // => 5

    let log2_100 = (64 - 1) - 100u64.next_power_of_two().leading_zeros();
    println!("ceil(log_2 100) = {}", log2_100); // => 7
}

[droundy]

I'll add that if you're explicitly looking for a power of two, you can just use the bit shift operator 1 << 32.