imperative vs declarative loop - a case where the traditional for loop is easier to read AND write

dedup.rs

    fn iterative_save<W: Write>(&self, mut wtr: W) -> Result<&Self> {
        for row in self {
            for (i, col) in row.iter().enumerate() {
                match i {
                    0 => wtr.write_all(col.as_bytes())?,
                    _ => {
                        wtr.write_all(b",")?;
                        wtr.write_all(col.as_bytes())?
                    }
                }
            }
            wtr.write_all(b"\n")?;
        }
        Ok(self)
    }

    fn declarative_save<W: Write>(&self, mut wtr: W) -> Result<&Self> {
        self.iter().try_for_each(|row| {
            row.iter().enumerate().try_for_each(|(i, col)| match i {
                0 => wtr.write_all(col.as_bytes()),
                _ => wtr
                    .write_all(b",")
                    .and_then(|_| wtr.write_all(col.as_bytes())),
            })?;
            wtr.write_all(b"\n")
        })?;

        Ok(self)
    }