diff --git a/src/crisp/evaluator.cr b/src/crisp/evaluator.cr
new file mode 100644
index 0000000..3ec131b
--- /dev/null
+++ b/src/crisp/evaluator.cr
@@ -0,0 +1,233 @@
+require "colorize"
+require "readline"
+
+require "./reader"
+require "./printer"
+require "./types"
+require "./env"
+require "./core"
+require "./error"
+
+module Crisp
+
+  class Evaluator
+    def func_of(env, binds, body)
+      -> (args : Array(Crisp::Type)) {
+      new_env = Crisp::Env.new(env, binds, args)
+      eval(body, new_env)
+      } as Crisp::Func
+    end
+
+    def eval_ast(ast, env)
+      return ast.map{|n| eval(n, env) as Crisp::Type} if ast.is_a? Array
+
+      val = ast.unwrap
+
+      Crisp::Type.new case val
+      when Crisp::Symbol
+        if e = env.get(val.str)
+            e
+        else
+            Crisp.eval_error "'#{val.str}' not found"
+        end
+      when Crisp::List
+        val.each_with_object(Crisp::List.new){|n, l| l << eval(n, env)}
+      when Crisp::Vector
+        val.each_with_object(Crisp::Vector.new){|n, l| l << eval(n, env)}
+      when Crisp::HashMap
+        new_map = Crisp::HashMap.new
+        val.each{|k, v| new_map[k] = eval(v, env)}
+        new_map
+      else
+        val
+      end
+    end
+
+    macro pair?(list)
+      {{list}}.is_a?(Array) && !{{list}}.empty?
+    end
+
+    def quasiquote(ast)
+      list = ast.unwrap
+
+      unless pair?(list)
+      return Crisp::Type.new(
+        Crisp::List.new << gen_type(Crisp::Symbol, "quote") << ast
+      )
+      end
+
+      head = list.first.unwrap
+
+      case
+      # ("unquote" ...)
+      when head.is_a?(Crisp::Symbol) && head.str == "unquote"
+        list[1]
+      # (("splice-unquote" ...) ...)
+      when pair?(head) && (arg0 = head.first.unwrap).is_a?(Crisp::Symbol) && arg0.str == "splice-unquote"
+        tail = Crisp::Type.new list[1..-1].to_crisp_value
+        Crisp::Type.new(
+          Crisp::List.new << gen_type(Crisp::Symbol, "concat") << head[1] << quasiquote(tail)
+        )
+      else
+        tail = Crisp::Type.new list[1..-1].to_crisp_value
+        Crisp::Type.new(
+          Crisp::List.new << gen_type(Crisp::Symbol, "cons") << quasiquote(list.first) << quasiquote(tail)
+        )
+      end
+    end
+
+    def macro_call?(ast, env)
+      list = ast.unwrap
+      return false unless list.is_a? Crisp::List
+      return false if list.empty?
+
+      sym = list.first.unwrap
+      return false unless sym.is_a? Crisp::Symbol
+
+      func = env.find(sym.str).try(&.data[sym.str])
+      return false unless func && func.macro?
+
+      true
+    end
+
+    def macroexpand(ast, env)
+      while macro_call?(ast, env)
+
+        # Already checked in macro_call?
+        list = ast.unwrap as Crisp::List
+        func_sym = list[0].unwrap as Crisp::Symbol
+        func = env.get(func_sym.str).unwrap
+
+        case func
+        when Crisp::Func
+          ast = func.call(list[1..-1])
+        when Crisp::Closure
+          ast = func.fn.call(list[1..-1])
+        else
+          Crisp.eval_error "macro '#{func_sym.str}' must be function: #{ast}"
+        end
+      end
+
+      ast
+    end
+
+    macro invoke_list(l, env)
+      f = eval({{l}}.first, {{env}}).unwrap
+      args = eval_ast({{l}}[1..-1], {{env}}) as Array
+
+      case f
+      when Crisp::Closure
+        ast = f.ast
+        {{env}} = Crisp::Env.new(f.env, f.params, args)
+        next # TCO
+      when Crisp::Func
+        return f.call args
+      else
+        Crisp.eval_error "expected function as the first argument: #{f}"
+      end
+    end
+
+    def debug(ast)
+      puts print(ast).colorize.red
+    end
+
+    def eval(ast, env)
+      # 'next' in 'do...end' has a bug in crystal 0.7.1
+      # https://github.com/manastech/crystal/issues/659
+      while true
+        return eval_ast(ast, env) unless ast.unwrap.is_a? Crisp::List
+
+        ast = macroexpand(ast, env)
+
+        list = ast.unwrap
+
+        return ast unless list.is_a? Crisp::List
+        return ast if list.empty?
+
+        head = list.first.unwrap
+
+        return invoke_list(list, env) unless head.is_a? Crisp::Symbol
+
+        return Crisp::Type.new case head.str
+          when "def!"
+            Crisp.eval_error "wrong number of argument for 'def!'" unless list.size == 3
+            a1 = list[1].unwrap
+            Crisp.eval_error "1st argument of 'def!' must be symbol: #{a1}" unless a1.is_a? Crisp::Symbol
+            env.set(a1.str, eval(list[2], env))
+          when "let*"
+            Crisp.eval_error "wrong number of argument for 'def!'" unless list.size == 3
+
+            bindings = list[1].unwrap
+            Crisp.eval_error "1st argument of 'let*' must be list or vector" unless bindings.is_a? Array
+            Crisp.eval_error "size of binding list must be even" unless bindings.size.even?
+
+            new_env = Crisp::Env.new env
+            bindings.each_slice(2) do |binding|
+              key, value = binding
+              name = key.unwrap
+              Crisp.eval_error "name of binding must be specified as symbol #{name}" unless name.is_a? Crisp::Symbol
+              new_env.set(name.str, eval(value, new_env))
+            end
+
+            ast, env = list[2], new_env
+            next # TCO
+          when "do"
+            if list.empty?
+              ast = Crisp::Type.new nil
+              next
+            end
+
+            eval_ast(list[1..-2].to_crisp_value, env)
+            ast = list.last
+            next # TCO
+          when "if"
+            ast = unless eval(list[1], env).unwrap
+              list.size >= 4 ? list[3] : Crisp::Type.new(nil)
+            else
+              list[2]
+            end
+            next # TCO
+          when "fn*"
+            params = list[1].unwrap
+            unless params.is_a? Array
+              Crisp.eval_error "'fn*' parameters must be list or vector: #{params}"
+            end
+            Crisp::Closure.new(list[2], params, env, func_of(env, params, list[2]))
+          when "quote"
+            list[1]
+          when "quasiquote"
+            ast = quasiquote list[1]
+            next # TCO
+          when "defmacro!"
+            Crisp.eval_error "wrong number of argument for 'defmacro!'" unless list.size == 3
+            a1 = list[1].unwrap
+            Crisp.eval_error "1st argument of 'defmacro!' must be symbol: #{a1}" unless a1.is_a? Crisp::Symbol
+            env.set(a1.str, eval(list[2], env).tap{|n| n.is_macro = true})
+          when "macroexpand"
+            macroexpand(list[1], env)
+          when "try*"
+            catch_list = list[2].unwrap
+            return eval(list[1], env) unless catch_list.is_a? Crisp::List
+
+            catch_head = catch_list.first.unwrap
+            return eval(list[1], env) unless catch_head.is_a? Crisp::Symbol
+            return eval(list[1], env) unless catch_head.str == "catch*"
+
+            begin
+              eval(list[1], env)
+            rescue e : Crisp::RuntimeException
+              new_env = Crisp::Env.new(env, [catch_list[1]], [e.thrown])
+              eval(catch_list[2], new_env)
+            rescue e
+              new_env = Crisp::Env.new(env, [catch_list[1]], [Crisp::Type.new e.message])
+              eval(catch_list[2], new_env)
+            end
+          else
+            invoke_list(list, env)
+          end
+      end
+    end
+
+  end
+
+end
diff --git a/src/crisp/interpreter.cr b/src/crisp/interpreter.cr
index 6416ba1..ffea0f8 100644
--- a/src/crisp/interpreter.cr
+++ b/src/crisp/interpreter.cr
@@ -7,19 +7,18 @@ require "./types"
 require "./env"
 require "./core"
 require "./error"
-
-# Note:
-# Employed downcase names because Crystal prohibits uppercase names for methods
+require "./evaluator"
 
 module Crisp
 
   class Interpreter
     def initialize(args = nil)
       @printer = Printer.new
+      @evaluator = Evaluator.new
       @env = Crisp::Env.new
 
       Crisp::NameSpace.each{|k,v| @env.set(k, Crisp::Type.new(v))}
-      @env.set("eval", Crisp::Type.new -> (args: Array(Crisp::Type)){ eval(args[0], @env) })
+      @env.set("eval", Crisp::Type.new -> (args: Array(Crisp::Type)){ @evaluator.eval(args[0], @env) })
 
       eval_string "(def! not (fn* (a) (if a false true)))"
       eval_string "(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))"
@@ -38,233 +37,16 @@ module Crisp
       @env.set("*ARGV*", Crisp::Type.new argv)
     end
 
-    def func_of(env, binds, body)
-      -> (args : Array(Crisp::Type)) {
-      new_env = Crisp::Env.new(env, binds, args)
-      eval(body, new_env)
-      } as Crisp::Func
-    end
-
-    def eval_ast(ast, env)
-      return ast.map{|n| eval(n, env) as Crisp::Type} if ast.is_a? Array
-
-      val = ast.unwrap
-
-      Crisp::Type.new case val
-      when Crisp::Symbol
-        if e = env.get(val.str)
-            e
-        else
-            Crisp.eval_error "'#{val.str}' not found"
-        end
-      when Crisp::List
-        val.each_with_object(Crisp::List.new){|n, l| l << eval(n, env)}
-      when Crisp::Vector
-        val.each_with_object(Crisp::Vector.new){|n, l| l << eval(n, env)}
-      when Crisp::HashMap
-        new_map = Crisp::HashMap.new
-        val.each{|k, v| new_map[k] = eval(v, env)}
-        new_map
-      else
-        val
-      end
-    end
-
     def read(str)
       Crisp.read_str str
     end
 
-    macro pair?(list)
-      {{list}}.is_a?(Array) && !{{list}}.empty?
-    end
-
-    def quasiquote(ast)
-      list = ast.unwrap
-
-      unless pair?(list)
-      return Crisp::Type.new(
-        Crisp::List.new << gen_type(Crisp::Symbol, "quote") << ast
-      )
-      end
-
-      head = list.first.unwrap
-
-      case
-      # ("unquote" ...)
-      when head.is_a?(Crisp::Symbol) && head.str == "unquote"
-        list[1]
-      # (("splice-unquote" ...) ...)
-      when pair?(head) && (arg0 = head.first.unwrap).is_a?(Crisp::Symbol) && arg0.str == "splice-unquote"
-        tail = Crisp::Type.new list[1..-1].to_crisp_value
-        Crisp::Type.new(
-          Crisp::List.new << gen_type(Crisp::Symbol, "concat") << head[1] << quasiquote(tail)
-        )
-      else
-        tail = Crisp::Type.new list[1..-1].to_crisp_value
-        Crisp::Type.new(
-          Crisp::List.new << gen_type(Crisp::Symbol, "cons") << quasiquote(list.first) << quasiquote(tail)
-        )
-      end
-    end
-
-    def macro_call?(ast, env)
-      list = ast.unwrap
-      return false unless list.is_a? Crisp::List
-      return false if list.empty?
-
-      sym = list.first.unwrap
-      return false unless sym.is_a? Crisp::Symbol
-
-      func = env.find(sym.str).try(&.data[sym.str])
-      return false unless func && func.macro?
-
-      true
-    end
-
-    def macroexpand(ast, env)
-      while macro_call?(ast, env)
-
-        # Already checked in macro_call?
-        list = ast.unwrap as Crisp::List
-        func_sym = list[0].unwrap as Crisp::Symbol
-        func = env.get(func_sym.str).unwrap
-
-        case func
-        when Crisp::Func
-          ast = func.call(list[1..-1])
-        when Crisp::Closure
-          ast = func.fn.call(list[1..-1])
-        else
-          Crisp.eval_error "macro '#{func_sym.str}' must be function: #{ast}"
-        end
-      end
-
-      ast
-    end
-
-    macro invoke_list(l, env)
-      f = eval({{l}}.first, {{env}}).unwrap
-      args = eval_ast({{l}}[1..-1], {{env}}) as Array
-
-      case f
-      when Crisp::Closure
-        ast = f.ast
-        {{env}} = Crisp::Env.new(f.env, f.params, args)
-        next # TCO
-      when Crisp::Func
-        return f.call args
-      else
-        Crisp.eval_error "expected function as the first argument: #{f}"
-      end
-    end
-
-    def debug(ast)
-      puts print(ast).colorize.red
-    end
-
-    def eval(ast, env)
-      # 'next' in 'do...end' has a bug in crystal 0.7.1
-      # https://github.com/manastech/crystal/issues/659
-      while true
-        return eval_ast(ast, env) unless ast.unwrap.is_a? Crisp::List
-
-        ast = macroexpand(ast, env)
-
-        list = ast.unwrap
-
-        return ast unless list.is_a? Crisp::List
-        return ast if list.empty?
-
-        head = list.first.unwrap
-
-        return invoke_list(list, env) unless head.is_a? Crisp::Symbol
-
-        return Crisp::Type.new case head.str
-          when "def!"
-            Crisp.eval_error "wrong number of argument for 'def!'" unless list.size == 3
-            a1 = list[1].unwrap
-            Crisp.eval_error "1st argument of 'def!' must be symbol: #{a1}" unless a1.is_a? Crisp::Symbol
-            env.set(a1.str, eval(list[2], env))
-          when "let*"
-            Crisp.eval_error "wrong number of argument for 'def!'" unless list.size == 3
-
-            bindings = list[1].unwrap
-            Crisp.eval_error "1st argument of 'let*' must be list or vector" unless bindings.is_a? Array
-            Crisp.eval_error "size of binding list must be even" unless bindings.size.even?
-
-            new_env = Crisp::Env.new env
-            bindings.each_slice(2) do |binding|
-              key, value = binding
-              name = key.unwrap
-              Crisp.eval_error "name of binding must be specified as symbol #{name}" unless name.is_a? Crisp::Symbol
-              new_env.set(name.str, eval(value, new_env))
-            end
-
-            ast, env = list[2], new_env
-            next # TCO
-          when "do"
-            if list.empty?
-              ast = Crisp::Type.new nil
-              next
-            end
-
-            eval_ast(list[1..-2].to_crisp_value, env)
-            ast = list.last
-            next # TCO
-          when "if"
-            ast = unless eval(list[1], env).unwrap
-              list.size >= 4 ? list[3] : Crisp::Type.new(nil)
-            else
-              list[2]
-            end
-            next # TCO
-          when "fn*"
-            params = list[1].unwrap
-            unless params.is_a? Array
-              Crisp.eval_error "'fn*' parameters must be list or vector: #{params}"
-            end
-            Crisp::Closure.new(list[2], params, env, func_of(env, params, list[2]))
-          when "quote"
-            list[1]
-          when "quasiquote"
-            ast = quasiquote list[1]
-            next # TCO
-          when "defmacro!"
-            Crisp.eval_error "wrong number of argument for 'defmacro!'" unless list.size == 3
-            a1 = list[1].unwrap
-            Crisp.eval_error "1st argument of 'defmacro!' must be symbol: #{a1}" unless a1.is_a? Crisp::Symbol
-            env.set(a1.str, eval(list[2], env).tap{|n| n.is_macro = true})
-          when "macroexpand"
-            macroexpand(list[1], env)
-          when "try*"
-            catch_list = list[2].unwrap
-            return eval(list[1], env) unless catch_list.is_a? Crisp::List
-
-            catch_head = catch_list.first.unwrap
-            return eval(list[1], env) unless catch_head.is_a? Crisp::Symbol
-            return eval(list[1], env) unless catch_head.str == "catch*"
-
-            begin
-              eval(list[1], env)
-            rescue e : Crisp::RuntimeException
-              new_env = Crisp::Env.new(env, [catch_list[1]], [e.thrown])
-              eval(catch_list[2], new_env)
-            rescue e
-              new_env = Crisp::Env.new(env, [catch_list[1]], [Crisp::Type.new e.message])
-              eval(catch_list[2], new_env)
-            end
-          else
-            invoke_list(list, env)
-          end
-      end
-    end
-
     def print(result)
       @printer.print(result)
     end
 
     def eval_string(str)
-      print(eval(read(str), @env))
+      print(@evaluator.eval(read(str), @env))
     end
 
     def run(filename = nil)