Question

I’m working with Ripper sexp expressions, it looks like this:

[:program,
 [[:class,
   [:const_ref, [:@const, "A", [1, 6]]],
   nil,
   [:bodystmt,
    [[:class,
      [:const_ref, [:@const, "B", [1, 15]]],
      nil,
      [:bodystmt,
       [[:def,
         [:@ident, "test", [1, 22]],
         [:params, nil, nil, nil, nil, nil],
         [:bodystmt, [[:void_stmt]], nil, nil, nil]]],
       nil,
       nil,
       nil]]],
    nil,
    nil,
    nil]]]]

And i’m using array as path to get element in sexp expression. For example

path = [1,0,1,1]   =>   sexp[1][0][1][1]

will get me

[:@const, "A", [1, 6]]

With this path I can get next, previous, parent elements and so on.

But I’m wondering is there a data structure which more suitable for this kind of tasks?

Answer 1

Besides the obvious trees, you may want to look at zippers:

http://en.wikipedia.org/wiki/Zipper_(data_structure)

Someone recently implemented form-zip for Clojure, if you want to look at an example:

https://github.com/GeorgeJahad/form-zip