pub fn list(&self) -> Result<&Vec<Sexp>, SexpError> {
        match *self {
            Sexp::List(ref v) => Ok(v),
            _ => Err(format!("not a list: {}", self).into()),
        }
    }
/// access the symbolic-expression as if it is a List
access the symbolic-expression as if it is a List
access the symbolic - expression as if it is a List
pub fn list(&self) -> Result<&Vec<Sexp>, SexpError> {
        match *self {
            Sexp::List(ref v) => Ok(v),
            _ => Err(format!("not a list: {}", self).into()),
        }
    }
pub fn list ( & self ) -> Result < & Vec < Sexp > , SexpError > { match * self { Sexp :: List ( ref v ) => Ok ( v ) , _ => Err ( format ! ( " " self ) . into ( ) ) , } }
access the symbolic-expression as if it is a List
access the symbolic - expression as if it is a List
&self