purge_from() for a file.

gistfile1.rs

    fn move_to(&mut self, line: u64) {
        let mut lines_read = 0;
        let chars = self.log.chars();
        // Go until we've reached `from` new lines.
        chars.skip_while(|&opt| {
            match opt {
                Ok(val) => {
                    if val == '\n' {
                        lines_read += 1;
                        if lines_read == line {
                            false // At right location.
                        } else {
                            true // Not done yet, more lines to go.
                        }
                    } else {
                        true // Not a new line.
                    }
                },
                _ => false // At EOF. Nothing to purge.
            }
        });
    }

   Compiling raft v0.0.1 (file:///Users/hoverbear/git/raft)
src/lib.rs:605:21: 605:25 error: cannot move out of borrowed content
src/lib.rs:605         let chars = self.log.chars();
                                   ^~~~
src/lib.rs:607:27: 607:31 error: cannot move out of borrowed content
src/lib.rs:607         chars.skip_while(|&opt| {
                                         ^~~~
src/lib.rs:607:28: 607:31 note: attempting to move value to here
src/lib.rs:607         chars.skip_while(|&opt| {
                                          ^~~
src/lib.rs:607:28: 607:31 help: to prevent the move, use `ref opt` or `ref mut opt` to capture value by reference
src/lib.rs:607         chars.skip_while(|&opt| {
                                          ^~~
error: aborting due to 2 previous errors