more tweaks for correctness,

added more examples to make sure proper results are being interpreted

bin/ez-scheme

@@ -2,7 +2,7 @@ require 'ez-scheme/interpreter'
 
 if file = ARGV[0]
   inp = IO.read(file)
-  interpret_code(inp)
+  interactive_interpreter(interpret_code(inp))
 else
   interactive_interpreter()
 end

lib/ez-scheme/builtins.rb

@@ -90,7 +90,7 @@ def builtin_eqv(args)
   #
   left, right = args[0], args[1]
 
-  if left.instance_of(Pair) and right.instance_of(Pair)
+  if left.instance_of?(Pair) and right.instance_of?(Pair)
     Boolean.new(left.object_id == right.object_id)
   else
     Boolean.new(left == right)
@@ -134,16 +134,21 @@ def builtin_or(args)
 end
 
 def make_comparison_operator_builtin(op)
-    lambda{ |args|
+    Proc.new{ |args|
       a = args[0]
+      res = nil
       for b in args[1..-1]
-        if send(op, a.value, b.value)
+        if a.value.send(op, b.value)
           a = b
         else
-          return Boolean.new(false)
+          break res = Boolean.new(false)
         end
       end
-      Boolean.new(true)
+      if res
+        res
+      else
+        Boolean.new(true)
+      end
     }
 end
 

lib/ez-scheme/environment.rb

@@ -30,7 +30,8 @@ def lookup_var(var)
     elsif ! @parent.nil?
       return @parent.lookup_var(var)
     else
-      raise Unbound.new("unbound variable '#{var}'") 
+      return nil
+      #raise Unbound.new("unbound variable '#{var}'") 
     end           
   end
 

lib/ez-scheme/expr.rb

@@ -111,7 +111,8 @@ def repr_rec(obj)
     elsif obj.instance_of?(Array)
       obj.map {|o| repr_rec(o) }.join("\n")
     else
-      raise ExprError.new("Unexpected type: #{obj.class}")
+      obj.class.to_s
+      #raise ExprError.new("Unexpected type: #{obj.class}")
     end
   end
 
@@ -408,8 +409,8 @@ def convert_let_to_application(exp)
 
     bindings = let_bindings(exp)
     while ! bindings.nil?
-        vars.append(bindings.first.first)
-        vals.append(bindings.first.second.first)
+        vars << bindings.first.first
+        vals << bindings.first.second.first
         bindings = bindings.second
     end
     lambda_expr = make_lambda(make_nested_pairs(*vars), let_body(exp))

lib/ez-scheme/interpreter.rb

@@ -4,7 +4,7 @@
 require File.dirname(__FILE__) + '/builtins'
 require 'pp'
 
-DEBUG = true
+DEBUG = ENV['DEBUG']
 
 
 class Procedure
@@ -87,7 +87,6 @@ def _eval(expr, env)
     elsif is_begin(expr)
       return _eval_sequence(begin_actions(expr), env)
     elsif is_application(expr)
-      puts "eval apply"
       return _apply(_eval(application_operator(expr), env),
                     _list_of_values(application_operands(expr), env))
     else
@@ -123,22 +122,18 @@ def _list_of_values(exprs, env)
   def _apply(proc, args)
     # Standard Scheme apply (SICP 4.1.1)
     #
-    if DEBUG
-      puts("~~~~ Applying procedure #{proc}")
-      puts("     with args #{expr_repr(args)}")
-    end
-
     if proc.instance_of?(BuiltinProcedure)
       if DEBUG
         puts("~~~~ Applying builtin procedure: #{proc.name}")
+        puts("     with args #{expr_repr(args)}")
       end
       # The '' builtin gets the current output stream as a custom
       # argument
       #
       return proc.apply(expand_nested_pairs(args))  
     elsif proc.instance_of?(Procedure)
       if DEBUG
-        puts("~~~~ Applying procedure with args: #{proc.args}")
+        puts("~~~~ Applying procedure with args: #{expr_repr(proc.args)}")
         puts("     and body:\n#{expr_repr(proc.body)}")
       end
       return _eval_sequence(proc.body,
@@ -201,12 +196,13 @@ def interpret_code(code_str, output_stream=nil)
   for expr in parsed_exprs
     interp.interpret(expr)
   end
+  interp
 end
 
-def interactive_interpreter()
+def interactive_interpreter(interp=nil)
   # Interactive interpreter 
 
-  interp = ::SchemeInterpreter.new # by default output_stream is sys.stdout
+  interp ||= ::SchemeInterpreter.new # by default output_stream is sys.stdout
   parser = ::SchemeParser.new
   puts("Type a Scheme expression or 'quit'")