Function strfmt::strfmt_map

pub fn strfmt_map<F>(fmtstr: &str, f: &F) -> Result<String> where
    F: Fn(Formatter) -> Result<()>, 

UNSTABLE: the Formatter object is still considered unstable Do not use this function if you aren't willing to have changes forced on you!

format a string given the string and a closure that uses a Formatter