Computing Ceil of Log2 in Rust

I want to calculate the following in Rust:

Python Equivalent:

math.ceil(math.log(b+1, 2))

ceil(log_2 n+1)

I have tried:

a+1.log2() 
(a+1).log2() 

but I get the error use of unstable library feature 'int_log'. I don’t want to use an unstable library feature. What is the easiest way to calculate log2, without any external crates if possible?

>Solution :

Rust is very particular about the difference between ints and floats. You can’t just type a integer and expect it to be auto-casted automatically. Always add a . at the end for a float.

Seems like you attempted to call the function on a integer. Try this:

Try this:

(1.).log2().ceil()

or

(a as f32 + 1.).log2().ceil()

If you want the end result as a integer you can use as i32 at the end. If you want double precision floats replace f32 with f64.

Reference:

https://doc.rust-lang.org/std/primitive.f32.html#method.ceil

https://doc.rust-lang.org/std/primitive.f32.html#method.log2