use std::fmt;
pub fn comma_delimited<T: fmt::Display>(f: &mut fmt::Formatter, mut iter: impl Iterator<Item=T>) -> fmt::Result {
if let Some(part) = iter.next() {
fmt::Display::fmt(&part, f)?;
}
for part in iter {
f.write_str(", ")?;
fmt::Display::fmt(&part, f)?;
}
Ok(())
}