sometime after input ==5 a little slow

[xianghx]

I think you can determine the legality of the string before you complete it.
Segmentation according to an illegal character (such as : % = ,)

Ok, may be I find a reason: input no space.

for n in 1..101 {
    if n % 15 == 0 {
        println!("fizzbuzz");
    } else if n % 3 == 0 {
        println!("fizz");
    } else if n % 5 == 0 {
        println!("buzz");
    } else {
        println!("{}", n);
    }
}

like this : n%4==0 , no space.
p:Point,

and backspace a little delay.

How to set (setq company-idle-delay 0.5) in racer?