init code

nodes.rb

@@ -0,0 +1,70 @@
+
+
+class Program < Treetop::Runtime::SyntaxNode
+  def eval(env={})
+    exprs.inject(nil){ |last_env, exp|
+      exp.eval(env)
+    }
+  end
+
+  def exprs
+    [expression] + expressions.exprs
+  end
+
+end
+
+class Cons < Treetop::Runtime::SyntaxNode
+  def eval(env)
+    self
+  end
+
+end
+
+class CompoundProcedure < Treetop::Runtime::SyntaxNode
+
+  def initialize(env, args, body)
+    @env = env
+    @args = args.elements.map{ |arg| arg.name}
+    @body = body
+  end
+
+  def apply(*values)
+    raise SchemeSyntaxError.new("Parameter doesn't match") unless @args.size == values.size
+    @body.eval(extend_env(values))
+  end
+
+  def extend_env(values)
+    @env.merge([@args, values].transpose.
+               map{ |key, value| { key => value}}.
+               inject{|sum, value| sum.merge(value)})
+  end
+end
+
+
+class RubyProcedure < Treetop::Runtime::SyntaxNode
+
+  def initialize(env, args, body)
+    @env = env
+    @args = args.elements.map{ |arg| arg.name}
+    @body = body
+  end
+
+  def apply(*values)
+    raise SchemeSyntaxError.new("Parameter doesn't match") unless @args.size == values.size
+    @body.call(*values)
+  end
+
+  def add(x, y)
+    x + y
+  end
+
+
+  def extend_env(values)
+    @env.merge([@args, values].transpose.map{ |key, value| { key => value}}.
+      inject{|sum, value| sum.merge(value)})
+  end
+end
+
+
+class SchemeSyntaxError < Exception
+end