我想用float::consts::pi
初始化一些頂級常量。例如:如何用其他常量初始化頂級常量?
import float::consts::pi;
const pi2:float = pi*pi;
fn main() {
io::println(#fmt("pi^2=%.4f", pi2));
}
我得到這些錯誤:
pi2.rs:3:18: 3:20 error: constant contains unimplemented expression type
pi2.rs:3 const pi2:float = pi*pi;
^~
pi2.rs:3:21: 3:23 error: constant contains unimplemented expression type
pi2.rs:3 const pi2:float = pi*pi;
^~
編譯成功,如果我寫:
const pi2:float = 3.14*3.14;
但它不是,如果我定義我自己pi
:
const pi:float = 3.141592653589793;
const pi2:float = pi*pi;
我正在使用r烏斯季0.2。
更新。 Rust-0.3.1中的消息更友好,並確認該功能尚未實現。引用同一箱常數是now allowed:
$ rustc pi2.rs
pi2.rs:2:18: 2:20 error: paths in constants may only refer to crate-local constants
pi2.rs:2 const pi2:float = pi*pi;
^~
pi2.rs:2:21: 2:23 error: paths in constants may only refer to crate-local constants
pi2.rs:2 const pi2:float = pi*pi;
^~
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug
note: try running with RUST_LOG=rustc=0,::rt::backtrace to get further details and report the results to github.com/mozilla/rust/issues
謝謝,但這沒有幫助。 'pi'不是'c_float'。 – sastanin 2012-04-02 14:56:57