fn peek_char(&mut self) -> Option<char> {
        if let Some(c) = self.remaining.peek() {
            Some(*c)
        } else {
            None
        }
    }
/// Peek at the next character.
Peek at the next character.
Peek at the next character .
fn peek_char(&mut self) -> Option<char> {
        if let Some(c) = self.remaining.peek() {
            Some(*c)
        } else {
            None
        }
    }
fn peek_char ( & mut self ) -> Option < char > { if let Some ( c ) = self . remaining . peek ( ) { Some ( * c ) } else { None } }
Peek at the next character.
Peek at the next character .
&mut self