IMO, Tuple is dissimilar from hash in that the fields are both named and ordered (like a struct - that's why I call it an anonymous struct), where as hashes have no guarantee on the order of the fields...  in a way tuple is similar to alist.  CTOR and dtor are needed for properly acquire and release external resources - but this might not be the scheme way... I don't know for sure yet. yinso <div>On 5/31/07, Carl Eastlund <<a href="mailto:cce@ccs.neu.edu">cce@ccs.neu.edu</a>> wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> On 6/1/07, YC <<a href="mailto:yinso.chen@gmail.com">yinso.chen@gmail.com</a>> wrote: > Tuples differ from vectors that they are indexed both by name & numbers, but > if struct is a named vector, in that sense it won't really be different, > except struct is opaque and hence better for building AST than vector IMHO. Ok, you want tuples with labelled fields.  Now they sound more like hash tables on symbols or strings.  Are they anything beyond that? -- Carl Eastlund </blockquote></div>