如何在Rust中使用复数方法？

Question

I've been puzzling over the plural functionality in Rust's std::fmt module, but I need a concrete example to make it real.

The 0.9 documentation for it is half way down the page here: http://static.rust-lang.org/doc/0.9/std/fmt/index.html

Is this intended to be useful to pluralize words? For example, how would I use it to print:

This page has been visited 0 times.
This page has been visited 1 time.
This page has been visited 2 times.

I tried this, but I'm getting an error:

fn main() {
    let mut count = 0;
    let s1 = format!("This page has been visited {:d} {0, plural, one{time} other{times}}.", count);
    println(s1);
}

error: argument used to format with `d` was attempted to not be used for formatting

Answer 1

The error message is quite confusing, but apparently you can not use the same parameter for both format strings. That is, you can not use the parameter 0 ( count ) for both {:d} and {0, plural, one{time} other{times}} .

It is possible to work around this limitation by passing the parameter twice in the function:

let s1 = format!("This page has been visited {:d} {1, plural, one{time} other{times}}.", count, count);

Alternatively you can use # to put the value itself inside the plural formatting:

let s1 = format!("This page has been visited {0, plural, one{# time} other{# times}}.", count);