Macro sprintf 

macro_rules! sprintf {
    ($fmt:expr, $($arg:expr),*) => { ... };
}

Format a string. (Roughly equivalent to snprintf or asprintf in C)

Takes a printf-style format string format and a variable number of additional arguments.

use sprintf::sprintf;
let s = sprintf!("%s = %*d", "forty-two", 4, 42).unwrap();
assert_eq!(s, "forty-two =   42");

Wrapper around vsprintf.