Macro try_format 

macro_rules! try_format {
    ($($arg:tt)*) => { ... };
}

Creates a String using interpolation of runtime expressions.

The first argument try_format! receives is a format string. This must be a string literal. The power of the formatting string is in the {}s contained.

Additional parameters passed to try_format! replace the {}s within the formatting string in the order given unless named or positional parameters are used; see std::fmt for more information.

A common use for try_format! is concatenation and interpolation of strings.