Some docs

lib/ruby/README.md

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+# Ruby
+
+A representation of the ruby code.
+
+## Concrete Syntax tree
+
+Ruby is parsed by the parser gem (big thanks to whitequark). Own attempts at
+this task have failed utterly, because ruby is a _huge_ language (and not well
+defined at that)
+
+Alas, the parser gem creates an abstract syntax tree, meaning one class is used
+to represent all node types.
+
+Imho object oriented languages have a class system to do just that, ie represent
+what we may loosely call type here, ie the kind of statement.
+
+The ruby layer is really all about defining classes for every kind of statement,
+thus "typing" the syntax tree, and making it concrete.
+
+## to Vool
+
+In our nice layers, we are ont the way down to Vool, a simplified version of oo.
+
+It has proven handy to have this layer, so the code for transforming each object
+is in the class representing that object. (As one does in oo, again imho).
+
+## Parfait objects
+
+The compilation process ends up creating (parfait) objects to represent
+things like classes, types and constants. This is not done here yet, but in
+the vool layer.