Power expression in a constant

Asked May 25 '15 at 15:52

Active May 25 '15 at 15:55

Viewed 53 times

I have the following code

pub const EXP: u32 = 4;
pub const POW: u32 = 3u32.pow(EXP);

This fails to compile since I'm using an expression:

src/t.rs:4:22: 4:35 error: constant contains unimplemented expression type [E0019]
src/t.rs:4 pub const POW: u32 = 3u32.pow(EXP);
                                ^~~~~~~~~~~~~

Can I have this value (3 ** EXP) be a constant in any other way? I can only think, at the moment, to have a function

#[inline(always)]
pub fn POW() -> { 3u32.pow(EXP); }

but I was wondering if it can be done with the constants as well.

edited May 25 '15 at 15:55

Shepmaster

388,571
95
1,107
1,366

asked May 25 '15 at 15:52

jdferreira

1

Maybe a duplicate of http://stackoverflow.com/q/29250386/155423? – Shepmaster May 25 '15 at 15:56
Yes, this is an almost exact duplicate of that. – Vladimir Matveev May 25 '15 at 16:00
Oh! I had not realized we finally had a user with Mjolnir in the Rust tag! Gratz Vladimir :) – Matthieu M. May 25 '15 at 16:00
[This](http://rust-ci.org/Kimundi/lazy-static.rs/doc/lazy_static/) is a helpful crate for defining variables that get initialized at runtime. – squiguy May 25 '15 at 18:03

Power expression in a constant

0 Answers0