diff --git a/lib/asm/arm/builder_a.rb b/lib/asm/arm/builder_a.rb
index 77c0149c..90008a7b 100644
--- a/lib/asm/arm/builder_a.rb
+++ b/lib/asm/arm/builder_a.rb
@@ -50,7 +50,7 @@ module Asm
 
       # Build representation for source value
       def build_operand(arg)
-        if (arg.is_a?(Asm::Parser::NumLiteralArgNode))
+        if (arg.is_a?(Asm::NumLiteralArgNode))
           if (arg.value.fits_u8?)
             # no shifting needed
             @operand = arg.value
@@ -61,10 +61,10 @@ module Asm
           else
             raise Asm::AssemblyError.new(Asm::ERRSTR_NUMERIC_TOO_LARGE, arg)
           end
-        elsif (arg.is_a?(Asm::Parser::RegisterArgNode))
+        elsif (arg.is_a?(Asm::RegisterArgNode))
           @operand = reg_ref(arg)
           @i = 0
-        elsif (arg.is_a?(Asm::Parser::ShiftNode))
+        elsif (arg.is_a?(Asm::ShiftNode))
           rm_ref = reg_ref(arg.argument)
           @i = 0
           shift_op = {'lsl' => 0b000, 'lsr' => 0b010, 'asr' => 0b100,
@@ -75,12 +75,12 @@ module Asm
           end
       
           arg1 = arg.value
-          if (arg1.is_a?(Asm::Parser::NumLiteralArgNode))
+          if (arg1.is_a?(Asm::NumLiteralArgNode))
             if (arg1.value >= 32)
               raise Asm::AssemblyError.new('cannot shift by more than 31', arg1)
             end
             shift_imm = arg1.value
-          elsif (arg1.is_a?(Asm::Parser::RegisterArgNode))
+          elsif (arg1.is_a?(Asm::RegisterArgNode))
             shift_op |= 0x1;
             shift_imm = reg_ref(arg1) << 1
           elsif (arg.type == 'rrx')
diff --git a/lib/asm/arm/builder_b.rb b/lib/asm/arm/builder_b.rb
index f5faa444..6bba2914 100644
--- a/lib/asm/arm/builder_b.rb
+++ b/lib/asm/arm/builder_b.rb
@@ -31,13 +31,13 @@ module Asm
         a
       end
 
-      class MathReferenceArgNode < Asm::Parser::ReferenceArgNode
+      class MathReferenceArgNode < Asm::ReferenceArgNode
         attr_accessor :op, :right
       end
       def simplify_reference(arg)
         node = MathReferenceArgNode.new
 
-        if (arg.is_a?(Asm::Parser::MathNode))
+        if (arg.is_a?(Asm::MathNode))
           node.argument = arg.left
           node.op = arg.op
           node.right = arg.right
@@ -50,17 +50,17 @@ module Asm
 
       # Build representation for target address
       def build_operand(arg1)
-        if (arg1.is_a?(Asm::Parser::ReferenceArgNode))
+        if (arg1.is_a?(Asm::ReferenceArgNode))
           argr = simplify_reference(arg1.argument)
           arg = argr.argument
-          if (arg.is_a?(Asm::Parser::RegisterArgNode))
+          if (arg.is_a?(Asm::RegisterArgNode))
             @i = 0
             @pre_post_index = 1
             @w = 0
             @rn = reg_ref(arg)
             @operand = 0
     
-            if (argr.op and argr.right.is_a?(Asm::Parser::NumLiteralArgNode))
+            if (argr.op and argr.right.is_a?(Asm::NumLiteralArgNode))
               val = argr.right.value
               if (val < 0)
                 @add_offset = 0
@@ -78,7 +78,7 @@ module Asm
           else
             raise Asm::AssemblyError.new(Asm::ERRSTR_INVALID_ARG, arg)
           end
-        elsif (arg1.is_a?(Asm::Parser::LabelEquivAddrArgNode) or arg1.is_a?(Asm::Parser::NumEquivAddrArgNode))
+        elsif (arg1.is_a?(Asm::LabelEquivAddrArgNode) or arg1.is_a?(Asm::NumEquivAddrArgNode))
           @i = 0
           @pre_post_index = 1
           @w = 0
@@ -99,10 +99,10 @@ module Asm
               (inst_class << 12+4+4+1+1+1+1+1+1) | (cond << 12+4+4+1+1+1+1+1+1+2)
         if (@use_addrtable_reloc)
           closest_addrtable = Asm::Arm.closest_addrtable(as)
-          if (@addrtable_reloc_target.is_a?(Asm::Parser::LabelEquivAddrArgNode))
+          if (@addrtable_reloc_target.is_a?(Asm::LabelEquivAddrArgNode))
             obj = ast_asm.object_for_label(@addrtable_reloc_target.label, inst)
             ref_label = closest_addrtable.add_label(obj)
-          elsif (@addrtable_reloc_target.is_a?(Asm::Parser::NumEquivAddrArgNode))
+          elsif (@addrtable_reloc_target.is_a?(Asm::NumEquivAddrArgNode))
             ref_label = closest_addrtable.add_const(@addrtable_reloc_target.value)
           end
           as.add_relocation io.tell, ref_label, Asm::Arm::R_ARM_PC12,
diff --git a/lib/asm/arm/builder_d.rb b/lib/asm/arm/builder_d.rb
index deac6306..ff6ac4f0 100644
--- a/lib/asm/arm/builder_d.rb
+++ b/lib/asm/arm/builder_d.rb
@@ -29,7 +29,7 @@ module Asm
 
       # Build representation for source value
       def build_operand(arg)
-        if (arg.is_a?(Asm::Parser::RegisterListArgNode))
+        if (arg.is_a?(Asm::RegisterListArgNode))
           @operand = 0
           arg.registers.each do |reg_node|
             reg = reg_ref(reg_node)
diff --git a/lib/asm/arm/instruction.rb b/lib/asm/arm/instruction.rb
index 7868001a..005d10ec 100644
--- a/lib/asm/arm/instruction.rb
+++ b/lib/asm/arm/instruction.rb
@@ -121,14 +121,14 @@ module Asm
           a.write io, as
         when :b, :bl
           arg = args[0]
-          if (arg.is_a?(Asm::Parser::NumLiteralArgNode))
+          if (arg.is_a?(Asm::NumLiteralArgNode))
             jmp_val = arg.value >> 2
             packed = [jmp_val].pack('l')
             # signed 32-bit, condense to 24-bit
             # TODO add check that the value fits into 24 bits
             io << packed[0,3]
-          elsif (arg.is_a?(Asm::LabelObject) or arg.is_a?(Asm::Parser::LabelRefArgNode))
-            arg = @ast_asm.object_for_label(arg.label, self) if arg.is_a?(Asm::Parser::LabelRefArgNode)
+          elsif (arg.is_a?(Asm::LabelObject) or arg.is_a?(Asm::LabelRefArgNode))
+            arg = @ast_asm.object_for_label(arg.label, self) if arg.is_a?(Asm::LabelRefArgNode)
             as.add_relocation(io.tell, arg, Asm::Arm::R_ARM_PC24, RelocHandler)
             io << "\x00\x00\x00"
           end
@@ -139,7 +139,7 @@ module Asm
                           (COND_BITS[@cond] << 16+4+8)
         when :swi
           arg = args[0]
-          if (arg.is_a?(Asm::Parser::NumLiteralArgNode))
+          if (arg.is_a?(Asm::NumLiteralArgNode))
             packed = [arg.value].pack('L')[0,3]
             io << packed
             io.write_uint8 0b1111 | (COND_BITS[@cond] << 4)
diff --git a/lib/asm/arm/instruction_tools.rb b/lib/asm/arm/instruction_tools.rb
index 36585b79..eb52e74d 100644
--- a/lib/asm/arm/instruction_tools.rb
+++ b/lib/asm/arm/instruction_tools.rb
@@ -2,7 +2,7 @@ module Asm
   module Arm
     module Asm::Arm::InstructionTools
       def reg_ref(arg)
-        if (not arg.is_a?(Asm::Parser::RegisterArgNode))
+        if (not arg.is_a?(Asm::RegisterArgNode))
           raise Asm::AssemblyError.new('argument must be a register', arg)
         end
 
diff --git a/lib/asm/ast_assembler.rb b/lib/asm/ast_assembler.rb
index 2b4422fd..4fff46bd 100644
--- a/lib/asm/ast_assembler.rb
+++ b/lib/asm/ast_assembler.rb
@@ -16,17 +16,17 @@ module Asm
     def load_ast(ast)
       label_breadcrumb = []
       ast.children.each do |cmd|
-        if (cmd.is_a?(Asm::Parser::LabelNode))
+        if (cmd.is_a?(Asm::LabelNode))
           m = /^\/+/.match(cmd.name)
           count = m ? m[0].length : 0
           label_breadcrumb = label_breadcrumb[0,count]
           label_breadcrumb << cmd.name[count..-1]
           @asm.add_object object_for_label(label_breadcrumb.join('/'))
-        elsif (cmd.is_a?(Asm::Parser::InstructionNode))
+        elsif (cmd.is_a?(Asm::InstructionNode))
           inst = @asm_arch::Instruction.new(cmd, self)
           @asm.add_object inst
           @inst_label_context[inst] = label_breadcrumb
-        elsif (cmd.is_a?(Asm::Parser::DirectiveNode))
+        elsif (cmd.is_a?(Asm::DirectiveNode))
           if (cmd.name == 'global')
             symbol_for_label(cmd.value)[:linkage] = Elf::Constants::STB_GLOBAL
           elsif (cmd.name == 'extern')
diff --git a/lib/asm/nodes.rb b/lib/asm/nodes.rb
new file mode 100644
index 00000000..36013c0a
--- /dev/null
+++ b/lib/asm/nodes.rb
@@ -0,0 +1,80 @@
+module Asm
+
+  class Node
+    def initialize(s = nil)
+      if (s)
+        @line = s.prev_line
+        @column = s.prev_column
+      else
+        @line = 0
+        @column = 0
+      end
+
+      yield self if block_given?
+    end
+    attr_reader :line, :column
+  end
+
+  class ToplevelNode < Node
+    attr_accessor :children
+  end
+
+  class DirectiveNode < Node
+    attr_accessor :name, :value
+  end
+
+  class LabelNode < Node
+    attr_accessor :name
+  end
+
+  class InstructionNode < Node
+    attr_accessor :opcode, :args
+  end
+
+  class ArgNode < Node
+  end
+
+  class ShiftNode < Node
+    attr_accessor :type, :value, :argument
+  end
+
+  class MathNode < Node
+    attr_accessor :left, :right, :op
+    alias_method :argument, :left
+    alias_method :argument=, :left=
+  end
+
+  class RegisterArgNode < ArgNode
+    attr_accessor :name
+  end
+
+  class RegisterListArgNode < ArgNode
+    attr_accessor :registers
+  end
+
+  class NumLiteralArgNode < ArgNode
+    attr_accessor :value
+  end
+
+  class NumEquivAddrArgNode < NumLiteralArgNode
+  end
+  class LabelRefArgNode < ArgNode
+    attr_accessor :label, :label_object
+  end
+  class LabelEquivAddrArgNode < LabelRefArgNode
+  end
+
+  class ReferenceArgNode < ArgNode
+    attr_accessor :argument
+  end
+
+  class ParseError < StandardError
+    def initialize(message, s)
+      super(message)
+
+      @line = s.line
+      @column = s.column
+    end
+    attr_reader :line, :column
+  end
+end
diff --git a/lib/asm/parser.rb b/lib/asm/parser.rb
index 4a99cb81..4f703835 100644
--- a/lib/asm/parser.rb
+++ b/lib/asm/parser.rb
@@ -1,16 +1,7 @@
 require_relative 'str_scanner'
+require_relative 'nodes'
 
 module Asm
-  class ParseError < StandardError
-    def initialize(message, s)
-      super(message)
-
-      @line = s.line
-      @column = s.column
-    end
-    attr_reader :line, :column
-  end
-
   class Parser
     def initialize(str)
       scanner = Asm::Scanner.new(str)
@@ -23,24 +14,6 @@ module Asm
       new(str).ast
     end
 
-    class Node
-      def initialize(s = nil)
-        if (s)
-          @line = s.prev_line
-          @column = s.prev_column
-        else
-          @line = 0
-          @column = 0
-        end
-
-        yield self if block_given?
-      end
-      attr_reader :line, :column
-    end
-
-    class ToplevelNode < Node
-      attr_accessor :children
-    end
     def parse_toplevel(s)
       node = ToplevelNode.new(s)
       node.children = []
@@ -63,16 +36,12 @@ module Asm
       node
     end
 
-    class CommentNode < Node; end
     def parse_comment(s)
       if (s.scan(/;.*?$/))
         CommentNode.new(s)
       end
     end
 
-    class DirectiveNode < Node
-      attr_accessor :name, :value
-    end
     def parse_directive(s)
       if (m = s.scan(/\.(\w+)(?:(?!$)\s+(.+)\s*?$)?/))
         DirectiveNode.new(s) { |n|
@@ -82,9 +51,6 @@ module Asm
       end
     end
 
-    class LabelNode < Node
-      attr_accessor :name
-    end
     def parse_label(s)
       if (m = s.scan(/(\/*\w+):/))
         LabelNode.new(s) { |n|
@@ -93,9 +59,6 @@ module Asm
       end
     end
 
-    class InstructionNode < Node
-      attr_accessor :opcode, :args
-    end
     def parse_instruction(s)
       if (m = s.scan(/(\w+)/))
         node = InstructionNode.new(s) { |n|
@@ -113,8 +76,6 @@ module Asm
       end
     end
 
-    class ArgNode < Node
-    end
     def parse_arg(s)
       s.scan /\s*/
       node = nil
@@ -146,9 +107,6 @@ module Asm
       node
     end
 
-    class ShiftNode < Node
-      attr_accessor :type, :value, :argument
-    end
     def parse_shift(s)
       if (m = s.scan(/(lsl|lsr|asr|ror|rrx)\s+/i))
         op = m[0].downcase
@@ -163,11 +121,6 @@ module Asm
       end
     end
   
-    class MathNode < Node
-      attr_accessor :left, :right, :op
-      alias_method :argument, :left
-      alias_method :argument=, :left=
-    end
     def parse_math(s)
       if (m = s.scan_str(/[\+\-]/))
         if (arg1 = parse_arg(s))
@@ -185,9 +138,6 @@ module Asm
        r13 r14 r15 a1 a2 a3 a4 v1 v2 v3 v4 v5 v6
        rfp sl fp ip sp lr pc
     ))
-    class RegisterArgNode < ArgNode
-      attr_accessor :name
-    end
     def parse_register(s)
       if (m = s.scan_str(REGISTER_REGEXP))
         RegisterArgNode.new(s) { |n|
@@ -196,9 +146,6 @@ module Asm
       end
     end
   
-    class RegisterListArgNode < ArgNode
-      attr_accessor :registers
-    end
     def parse_register_list(s)
       if (m = s.scan(/\{/))
         node = RegisterListArgNode.new(s) do |n|
@@ -222,11 +169,6 @@ module Asm
       end
     end
 
-    class NumLiteralArgNode < ArgNode
-      attr_accessor :value
-    end
-    class NumEquivAddrArgNode < NumLiteralArgNode
-    end
     def parse_num_literal(s)
       if (m = s.scan(/(=?)#(-?(?:0x)?[0-9A-Fa-f]+)/))
         (m[0] == '=' ? NumEquivAddrArgNode : NumLiteralArgNode).new(s) { |n|
@@ -235,11 +177,6 @@ module Asm
       end
     end
 
-    class LabelRefArgNode < ArgNode
-      attr_accessor :label, :label_object
-    end
-    class LabelEquivAddrArgNode < LabelRefArgNode
-    end
     def parse_label_ref(s)
       if (m = s.scan(/(=?)(\/*\w+)/))
         (m[0] == '=' ? LabelEquivAddrArgNode : LabelRefArgNode).new(s) { |n|
@@ -248,9 +185,6 @@ module Asm
       end
     end
   
-    class ReferenceArgNode < ArgNode
-      attr_accessor :argument
-    end
     def parse_reference(s)
       if (m = s.scan(/\[/))
         arg = parse_arg(s)