work on nodes.coffee and adding scope.coffee

src/scope.coffee

@@ -0,0 +1,99 @@
+dup: (input) ->
+  output: null
+  if input instaceof Array
+    output: []
+    for val in input
+      output.push(val)
+  else
+    output: {}
+    for key, val of input
+      output.key: val
+    output
+  output
+
+# scope objects form a tree corresponding to the shape of the function 
+# definitions present in the script. They provide lexical scope, to determine 
+# whether a variable has been seen before or if it needs to be declared.
+exports.Scope: (parent, expressions, func) ->
+  # Initialize a scope with its parent, for lookups up the chain,
+  # as well as the Expressions body where it should declare its variables,
+  # and the function that it wraps.
+  this.parent: parent
+  this.expressions: expressions
+  this.function: func
+  this.variables: {}
+  this.temp_variable: if this.parent then dup(this.parent.temp_variable) : '__a'
+
+# Look up a variable in lexical scope, or declare it if not found.
+exports.Scope::find: (name, rem) ->
+  remote: if rem? then rem else false
+  found: this.check(name)
+  return found if found || remote
+  this.variables[name]: 'var'
+  found
+
+# Define a local variable as originating from a parameter in current scope
+# -- no var required.
+exports.Scope::parameter: (name) ->
+  this.variables[name]: = 'param'
+
+# Just check to see if a variable has already been declared.
+exports.Scope::check: (name) ->
+  return true if this.variables[name]?
+  # TODO: what does that ruby !! mean..? need to follow up
+  # .. this next line is prolly wrong ..
+  not not (this.parent and this.parent.check(name))
+
+# You can reset a found variable on the immediate scope.
+exports.Scope::reset: (name) ->
+  this.variables[name]: undefined
+
+exports.Scope::free_variable: ->
+  # need .succ! impl
+
+    # Find an available, short, name for a compiler-generated variable.
+    def free_variable
+      @temp_variable.succ! while check(@temp_variable)
+      @variables[@temp_variable.to_sym] = :var
+      Value.new(@temp_variable.dup)
+    end
+
+    # Ensure that an assignment is made at the top of scope (or top-level
+    # scope, if requested).
+    def assign(name, value, top=false)
+      return @parent.assign(name, value, top) if top && @parent
+      @variables[name.to_sym] = Value.new(value)
+    end
+
+    def declarations?(body)
+      !declared_variables.empty? && body == @expressions
+    end
+
+    def assignments?(body)
+      !assigned_variables.empty? && body == @expressions
+    end
+
+    # Return the list of variables first declared in current scope.
+    def declared_variables
+      @variables.select {|k, v| v == :var }.map {|pair| pair[0].to_s }.sort
+    end
+
+    # Return the list of variables that are supposed to be assigned at the top
+    # of scope.
+    def assigned_variables
+      @variables.select {|k, v| v.is_a?(Value) }.sort_by {|pair| pair[0].to_s }
+    end
+
+    def compiled_declarations
+      declared_variables.join(', ')
+    end
+
+    def compiled_assignments
+      assigned_variables.map {|name, val| "#{name} = #{val}"}.join(', ')
+    end
+
+    def inspect
+      "<Scope:#{__id__} #{@variables.inspect}>"
+    end
+
+  end