/ˈkɑːnstənt/
n. 常数，恒量；
b”Rust牛” byte constant must be ASCII
[adj.]
occurring continuously over a period of time
the pain is constent.
A constant guest is never welcome.常客令人厌。
remaining the same over a period of time
the company has kept its prices fairly constant.
(of a person) unchangingly failthful and dependable
constant if statement. satement can be simplified. 当if只有一个分支，且没有啥用的时候，就是constant if stagement.