Renaming Vool exppressions rightly

Class, Method and Lambda (was block) are expressions.
Just making things clearer, especially for the blocks (ahem, lambdas) is matters.
wip

lib/vool/statement.rb

@@ -2,7 +2,7 @@
 # Object Oriented
 # Language
 #
-# VOOL is the abstraction of ruby, ruby minus some of the fluff
+# VOOL is the abstraction of ruby, ruby minusthe fluff
 #      fluff is generally what makes ruby nice to use, like 3 ways to achieve the same thing
 #      if/unless/ternary , reverse ifs (ie statement if condition), reverse whiles,
 #      implicit blocks, splats and multiple assigns etc
@@ -10,19 +10,17 @@
 # Also, Vool is a typed tree, not abstract, so  there is a base class Statement
 #            and all it's derivation that make up the syntax tree
 #
-# Also Vool has expression and statements and simple syntax. So returns must be explicit
-# not everthing is just assignable, ifs can only test simple expressions etc (wip)
-#
-# This allows us to write compilers or passes of the compiler(s) as functions on the
-# classes.
-#
+# Also Vool has expression and statements, revealing that age old dichotomy of code and
+# data. Statements represent code whereas Expressions resolve to data.
+# (in ruby there are no pure statements, everthing resolves to data)
 module Vool
 
   # Base class for all statements in the tree. Derived classes correspond to known language
   # constructs
   #
-  # Compilers or compiler passes are written by implementing methods.
-  #
+  # Basically Statements represent code, generally speaking code "does things".
+  # But Vool distinguishes Expressions (see below), that represent data, and as such
+  # don't do things themselves, rather passively participate in being pushed around
   class Statement
 
     def to_mom( _ )
@@ -37,7 +35,13 @@ module Vool
 
   end
 
-  class Expression
+  # An Expression is a Statement that represents data. ie variables constants
+  # (see basic_values) , but alos classes, methods and lambdas
+  class Expression < Statement
+
+    def each(&block)
+      block.call(self)
+    end
 
     def ct_type
       nil
@@ -46,20 +50,13 @@ module Vool
     def normalize
       raise "should not be normalized #{self}"
     end
-    def to_mom(compiler)
-      raise "should not be momed #{self}"
-    end
 
-    # for loading into a lot, return the "slot_definition" that can be passed to
+    # for loading into a slot, return the "slot_definition" that can be passed to
     # SlotLoad.
-    def slot_definition(compiler)
+    def to_slot(compiler)
       raise "not iplemented in #{self}"
     end
 
-    def at_depth(depth , *strings)
-      prefix = " " * 2 * depth
-      strings.collect{|str| prefix + str}.join("\n")
-    end
   end
 
 end
@@ -67,14 +64,14 @@ end
 
 require_relative "assignment"
 require_relative "basic_values"
-require_relative "block_statement"
 require_relative "call_statement"
-require_relative "class_statement"
+require_relative "class_expression"
 require_relative "if_statement"
 require_relative "ivar_assignment"
+require_relative "lambda_expression"
 require_relative "local_assignment"
-require_relative "method_statement"
-require_relative "class_method_statement"
+require_relative "method_expression"
+require_relative "class_method_expression"
 require_relative "return_statement"
 require_relative "statements"
 require_relative "send_statement"