diff --git a/code_obj.lua b/code_obj.lua
index 0fcd34d..37ac55a 100644
--- a/code_obj.lua
+++ b/code_obj.lua
@@ -82,8 +82,8 @@ do
     is_code = true,
     append = function(self, ...)
       local n = select("#", ...)
-      local bits, indents = self.bits, self.indents
       local match = string.match
+      local bits = self.bits
       for i = 1, n do
         local _continue_0 = false
         repeat
@@ -98,27 +98,6 @@ do
           if type(b) ~= 'string' and not (type(b) == 'table' and b.is_code) then
             b = repr(b)
           end
-          if type(b) == 'string' then
-            local trailing_text, spaces = match(b, "\n(([ ]*)[^\n]*)$")
-            if trailing_text then
-              self.current_indent = #spaces
-              self.trailing_line_len = #trailing_text
-            else
-              self.trailing_line_len = self.trailing_line_len + #b
-            end
-          else
-            do
-              local trailing_text = match(tostring(b), "\n([^\n]*)$")
-              if trailing_text then
-                self.trailing_line_len = #trailing_text + self.current_indent
-              else
-                self.trailing_line_len = self.trailing_line_len + #tostring(b)
-              end
-            end
-            if self.current_indent ~= 0 then
-              indents[#bits] = self.current_indent
-            end
-          end
           _continue_0 = true
         until true
         if not _continue_0 then
@@ -126,11 +105,35 @@ do
         end
       end
       self.__str = nil
+      self._trailing_line_len = nil
+    end,
+    trailing_line_len = function(self)
+      if self._trailing_line_len == nil then
+        local bits, match = self.bits, string.match
+        local len = 0
+        for i = #bits, 1, -1 do
+          local b = bits[i]
+          if type(b) == 'string' then
+            do
+              local line = match(b, "\n([^\n]*)$")
+              if line then
+                return len + #line
+              else
+                len = len + #b
+              end
+            end
+          else
+            len = len + b:trailing_line_len()
+          end
+        end
+        self._trailing_line_len = len
+      end
+      return self._trailing_line_len
     end,
     concat_append = function(self, values, joiner, wrapping_joiner)
       wrapping_joiner = wrapping_joiner or joiner
-      local bits, indents = self.bits, self.indents
       local match = string.match
+      local bits = self.bits
       local line_len = 0
       for i = 1, #values do
         local b = values[i]
@@ -143,47 +146,28 @@ do
           end
         end
         bits[#bits + 1] = b
-        if type(b) ~= 'string' and self.current_indent ~= 0 then
-          indents[#bits] = self.current_indent
-        end
         local b_str = tostring(b)
-        local line, spaces = match(b_str, "\n(([ ]*)[^\n]*)$")
-        if spaces then
-          if type(b) == 'string' then
-            self.current_indent = #spaces
-          end
+        local line = match(b_str, "\n([^\n]*)$")
+        if line then
           line_len = #line
         else
           line_len = line_len + #b
         end
       end
       self.__str = nil
+      self._trailing_line_len = nil
     end,
     prepend = function(self, ...)
       local n = select("#", ...)
-      local bits, indents = self.bits, self.indents
+      local bits = self.bits
       for i = #bits + n, n + 1, -1 do
         bits[i] = bits[i - n]
       end
       for i = 1, n do
         bits[i] = select(i, ...)
       end
-      self.current_indent = 0
-      for i, b in ipairs(bits) do
-        if type(b) == 'string' then
-          do
-            local spaces = b:match("\n([ ]*)[^\n]*$")
-            if spaces then
-              self.current_indent = #spaces
-            end
-          end
-        elseif self.current_indent ~= 0 then
-          indents[i] = self.current_indent
-        else
-          indents[i] = nil
-        end
-      end
       self.__str = nil
+      self._trailing_line_len = nil
     end
   }
   _base_0.__index = _base_0
@@ -191,8 +175,6 @@ do
     __init = function(self, source, ...)
       self.source = source
       self.bits = { }
-      self.indents, self.current_indent = { }, 0
-      self.trailing_line_len = 0
       if type(self.source) == 'string' then
         self.source = Source:from_string(self.source)
       end
@@ -242,6 +224,7 @@ do
         end
       end
       self.__str = nil
+      self._trailing_line_len = nil
     end,
     remove_free_vars = function(self, vars)
       if not (#vars > 0) then
@@ -274,6 +257,7 @@ do
         end
       end
       self.__str = nil
+      self._trailing_line_len = nil
     end,
     declare_locals = function(self, to_declare)
       if to_declare == nil then
@@ -336,11 +320,25 @@ do
     end,
     __tostring = function(self)
       if self.__str == nil then
-        local buff, indents = { }, self.indents
+        local buff, indent = { }, 0
+        local match, gsub, rep
+        do
+          local _obj_0 = string
+          match, gsub, rep = _obj_0.match, _obj_0.gsub, _obj_0.rep
+        end
         for i, b in ipairs(self.bits) do
-          b = tostring(b)
-          if indents[i] then
-            b = b:gsub("\n", "\n" .. ((" "):rep(indents[i])))
+          if type(b) == 'string' then
+            do
+              local spaces = match(b, "\n([ ]*)[^\n]*$")
+              if spaces then
+                indent = #spaces
+              end
+            end
+          else
+            b = tostring(b)
+            if indent > 0 then
+              b = gsub(b, "\n", "\n" .. rep(" ", indent))
+            end
           end
           buff[#buff + 1] = b
         end
@@ -394,7 +392,6 @@ do
       _class_0.__parent.__init(self, ...)
       self.free_vars = { }
       self.is_value = false
-      self.__str = nil
     end,
     __base = _base_0,
     __name = "LuaCode",
@@ -424,11 +421,6 @@ do
     lua.is_value = true
     return lua
   end
-  self.Comment = function(...)
-    local lua = LuaCode(...)
-    lua.is_comment = true
-    return lua
-  end
   if _parent_0.__inherited then
     _parent_0.__inherited(_parent_0, _class_0)
   end
@@ -440,11 +432,25 @@ do
   local _base_0 = {
     __tostring = function(self)
       if self.__str == nil then
-        local buff, indents = { }, self.indents
+        local buff, indent = { }, 0
+        local match, gsub, rep
+        do
+          local _obj_0 = string
+          match, gsub, rep = _obj_0.match, _obj_0.gsub, _obj_0.rep
+        end
         for i, b in ipairs(self.bits) do
-          b = tostring(b)
-          if indents[i] then
-            b = b:gsub("\n", "\n" .. ((" "):rep(indents[i])))
+          if type(b) == 'string' then
+            do
+              local spaces = match(b, "\n([ ]*)[^\n]*$")
+              if spaces then
+                indent = #spaces
+              end
+            end
+          else
+            b = tostring(b)
+            if indent > 0 then
+              b = gsub(b, "\n", "\n" .. rep(" ", indent))
+            end
           end
           buff[#buff + 1] = b
         end
diff --git a/code_obj.moon b/code_obj.moon
index 5397cf6..e1cf226 100644
--- a/code_obj.moon
+++ b/code_obj.moon
@@ -48,8 +48,6 @@ class Code
     is_code: true
     new: (@source, ...)=>
         @bits = {}
-        @indents, @current_indent = {}, 0
-        @trailing_line_len = 0
         if type(@source) == 'string'
             @source = Source\from_string(@source)
         assert(@source and Source\is_instance(@source), "Source has the wrong type")
@@ -57,8 +55,8 @@ class Code
             
     append: (...)=>
         n = select("#",...)
-        bits, indents = @bits, @indents
         match = string.match
+        bits = @bits
         for i=1,n
             b = select(i, ...)
             assert(b, "code bit is nil")
@@ -67,24 +65,28 @@ class Code
             bits[#bits+1] = b
             if type(b) != 'string' and not (type(b) == 'table' and b.is_code)
                 b = repr(b)
-            if type(b) == 'string'
-                trailing_text, spaces = match(b, "\n(([ ]*)[^\n]*)$")
-                if trailing_text
-                    @current_indent = #spaces
-                    @trailing_line_len = #trailing_text
-                else @trailing_line_len += #b
-            else
-                if trailing_text = match(tostring(b), "\n([^\n]*)$")
-                    @trailing_line_len = #trailing_text + @current_indent
-                else @trailing_line_len += #tostring(b)
-                if @current_indent != 0
-                    indents[#bits] = @current_indent
         @__str = nil
+        @_trailing_line_len = nil
+    
+    trailing_line_len: =>
+        if @_trailing_line_len == nil
+            bits, match = @bits, string.match
+            len = 0
+            for i=#bits,1,-1
+                b = bits[i]
+                if type(b) == 'string'
+                    if line = match(b, "\n([^\n]*)$")
+                        return len + #line
+                    else len += #b
+                else
+                    len += b\trailing_line_len!
+            @_trailing_line_len = len
+        return @_trailing_line_len
             
     concat_append: (values, joiner, wrapping_joiner)=>
         wrapping_joiner or= joiner
-        bits, indents = @bits, @indents
         match = string.match
+        bits = @bits
         line_len = 0
         for i=1,#values
             b = values[i]
@@ -95,51 +97,35 @@ class Code
                 else
                     bits[#bits+1] = joiner
             bits[#bits+1] = b
-            if type(b) != 'string' and @current_indent != 0
-                indents[#bits] = @current_indent
             b_str = tostring(b)
-            line, spaces = match(b_str, "\n(([ ]*)[^\n]*)$")
-            if spaces
-                if type(b) == 'string'
-                    @current_indent = #spaces
+            line = match(b_str, "\n([^\n]*)$")
+            if line
                 line_len = #line
             else
                 line_len += #b
         @__str = nil
+        @_trailing_line_len = nil
     
     prepend: (...)=>
         n = select("#",...)
-        bits, indents = @bits, @indents
+        bits = @bits
         for i=#bits+n,n+1,-1
             bits[i] = bits[i-n]
         for i=1,n
             bits[i] = select(i, ...)
-        @current_indent = 0
-        for i,b in ipairs(bits)
-            if type(b) == 'string'
-                if spaces = b\match("\n([ ]*)[^\n]*$")
-                    @current_indent = #spaces
-            elseif @current_indent != 0
-                indents[i] = @current_indent
-            else indents[i] = nil
         @__str = nil
+        @_trailing_line_len = nil
 
 class LuaCode extends Code
     new: (...)=>
         super ...
         @free_vars = {}
         @is_value = false
-        @__str = nil
     
     @Value = (...)->
         lua = LuaCode(...)
         lua.is_value = true
         return lua
-    
-    @Comment = (...)->
-        lua = LuaCode(...)
-        lua.is_comment = true
-        return lua
 
     add_free_vars: (vars)=>
         return unless #vars > 0
@@ -150,6 +136,7 @@ class LuaCode extends Code
                 @free_vars[#@free_vars+1] = var
                 seen[var] = true
         @__str = nil
+        @_trailing_line_len = nil
     
     remove_free_vars: (vars)=>
         return unless #vars > 0
@@ -169,6 +156,7 @@ class LuaCode extends Code
                 if type(b) != 'string'
                     stack[#stack+1] = b
         @__str = nil
+        @_trailing_line_len = nil
 
     declare_locals: (to_declare=nil)=>
         if to_declare == nil
@@ -205,11 +193,16 @@ class LuaCode extends Code
 
     __tostring: =>
         if @__str == nil
-            buff, indents = {}, @indents
+            buff, indent = {}, 0
+            {:match, :gsub, :rep} = string
             for i,b in ipairs @bits
-                b = tostring(b)
-                if indents[i]
-                    b = b\gsub("\n", "\n"..((" ")\rep(indents[i])))
+                if type(b) == 'string'
+                    if spaces = match(b, "\n([ ]*)[^\n]*$")
+                        indent = #spaces
+                else
+                    b = tostring(b)
+                    if indent > 0
+                        b = gsub(b, "\n", "\n"..rep(" ", indent))
                 buff[#buff+1] = b
             @__str = concat(buff, "")
         return @__str
@@ -246,11 +239,16 @@ class LuaCode extends Code
 class NomsuCode extends Code
     __tostring: =>
         if @__str == nil
-            buff, indents = {}, @indents
+            buff, indent = {}, 0
+            {:match, :gsub, :rep} = string
             for i,b in ipairs @bits
-                b = tostring(b)
-                if indents[i]
-                    b = b\gsub("\n", "\n"..((" ")\rep(indents[i])))
+                if type(b) == 'string'
+                    if spaces = match(b, "\n([ ]*)[^\n]*$")
+                        indent = #spaces
+                else
+                    b = tostring(b)
+                    if indent > 0
+                        b = gsub(b, "\n", "\n"..rep(" ", indent))
                 buff[#buff+1] = b
             @__str = concat(buff, "")
         return @__str
diff --git a/files.lua b/files.lua
index fe1263e..65a8e1b 100644
--- a/files.lua
+++ b/files.lua
@@ -34,25 +34,52 @@ files.read = function(filename)
   _FILE_CACHE[filename] = contents
   return contents
 end
-local iterate_single
-iterate_single = function(item, prev)
-  if item == prev then
-    return nil
-  else
-    return item
-  end
-end
 local match, gsub
 do
   local _obj_0 = string
   match, gsub = _obj_0.match, _obj_0.gsub
 end
-iterate_single = function(item, prev)
-  if item == prev then
-    return nil
-  else
-    return item
+local sanitize
+sanitize = function(path)
+  path = gsub(path, "\\", "\\\\")
+  path = gsub(path, "`", "")
+  path = gsub(path, '"', '\\"')
+  path = gsub(path, "$", "")
+  return path
+end
+files.exists = function(path)
+  if not (io.popen("ls " .. tostring(sanitize(path))):close()) then
+    return true
   end
+  if package.nomsupath then
+    for nomsupath in package.nomsupath:gmatch("[^;]+") do
+      if not (io.popen("ls " .. tostring(nomsupath) .. "/" .. tostring(sanitize(path))):close()) then
+        return true
+      end
+    end
+  end
+  return false
+end
+local _browse_cache = { }
+local browse
+browse = function(path)
+  if not (_browse_cache[path]) then
+    local f = io.popen('find -L "' .. package.nomsupath .. '/' .. path .. '" -not -path "*/\\.*" -type f -name "*.nom"')
+    local _files
+    do
+      local _tbl_0 = { }
+      for line in f:lines() do
+        local _key_0, _val_0 = line
+        _tbl_0[_key_0] = _val_0
+      end
+      _files = _tbl_0
+    end
+    if not (f:close()) then
+      _files = false
+    end
+    _browse_cache[path] = _files
+  end
+  return _browse_cache[path]
 end
 local ok, lfs = pcall(require, "lfs")
 if ok then
@@ -78,109 +105,76 @@ if ok then
     end
     return false
   end
-  local browse
   browse = function(filename)
-    local file_type, err = lfs.attributes(filename, 'mode')
-    if file_type == 'file' then
-      if match(filename, "%.nom$") or match(filename, "%.lua$") then
-        coroutine.yield(filename)
-        return true
-      end
-    elseif file_type == 'directory' or file_type == 'link' then
-      for subfile in lfs.dir(filename) do
-        if not (subfile == "." or subfile == "..") then
-          browse(filename .. "/" .. subfile)
+    if not (_browse_cache[filename]) then
+      _browse_cache[filename] = false
+      local file_type, err = lfs.attributes(filename, 'mode')
+      if file_type == 'file' then
+        if match(filename, "%.nom$") or match(filename, "%.lua$") then
+          _browse_cache[filename] = {
+            filename
+          }
         end
-      end
-      return true
-    elseif file_type == 'char device' then
-      coroutine.yield(filename)
-      return true
-    end
-    return false
-  end
-  files.walk = function(path)
-    if match(path, "%.nom$") or match(path, "%.lua$") or path == 'stdin' then
-      return iterate_single, path
-    end
-    return coroutine.wrap(function()
-      if not browse(path) and package.nomsupath then
-        for nomsupath in package.nomsupath:gmatch("[^;]+") do
-          if browse(nomsupath .. "/" .. path) then
-            break
+      elseif file_type == 'char device' then
+        _browse_cache[filename] = {
+          filename
+        }
+      elseif file_type == 'directory' or file_type == 'link' then
+        local _files = { }
+        for subfile in lfs.dir(filename) do
+          if not (subfile == "." or subfile == "..") then
+            local _list_0 = (browse(filename .. "/" .. subfile) or { })
+            for _index_0 = 1, #_list_0 do
+              local f = _list_0[_index_0]
+              _files[#_files + 1] = f
+            end
           end
         end
+        _browse_cache[filename] = _files
       end
-      return nil
-    end)
+    end
+    return _browse_cache[filename]
   end
 else
   if io.popen('find . -maxdepth 0'):close() then
     error("Could not find 'luafilesystem' module and couldn't run system command `find` (this might happen on Windows). Please install `luafilesystem` (which can be found at: http://keplerproject.github.io/luafilesystem/ or `luarocks install luafilesystem`)", 0)
   end
-  local sanitize
-  sanitize = function(path)
-    path = gsub(path, "\\", "\\\\")
-    path = gsub(path, "`", "")
-    path = gsub(path, '"', '\\"')
-    path = gsub(path, "$", "")
-    return path
+end
+files.walk = function(path, flush_cache)
+  if flush_cache == nil then
+    flush_cache = false
   end
-  files.exists = function(path)
-    if not (io.popen("ls " .. tostring(sanitize(path))):close()) then
-      return true
-    end
-    if package.nomsupath then
-      for nomsupath in package.nomsupath:gmatch("[^;]+") do
-        if not (io.popen("ls " .. tostring(nomsupath) .. "/" .. tostring(sanitize(path))):close()) then
-          return true
+  if flush_cache then
+    _browse_cache = { }
+  end
+  local _files = browse(path)
+  if package.nomsupath and not _files then
+    for nomsupath in package.nomsupath:gmatch("[^;]+") do
+      do
+        _files = browse(nomsupath .. "/" .. path)
+        if _files then
+          break
         end
       end
     end
-    return false
   end
-  files.walk = function(path)
-    if match(path, "%.nom$") or match(path, "%.lua$") or path == 'stdin' then
-      return iterate_single, path
+  local iter
+  iter = function(_files, i)
+    i = i + 1
+    do
+      local f = _files[i]
+      if f then
+        return i, f
+      end
     end
-    path = sanitize(path)
-    return coroutine.wrap(function()
-      local f = io.popen('find -L "' .. path .. '" -not -path "*/\\.*" -type f -name "*.nom"')
-      local found = false
-      for line in f:lines() do
-        found = true
-        coroutine.yield(line)
-      end
-      if not found and package.nomsupath then
-        f:close()
-        for nomsupath in package.nomsupath:gmatch("[^;]+") do
-          f = io.popen('find -L "' .. package.nomsupath .. '/' .. path .. '" -not -path "*/\\.*" -type f -name "*.nom"')
-          for line in f:lines() do
-            found = true
-            coroutine.yield(line)
-          end
-          f:close()
-          if found then
-            break
-          end
-        end
-      end
-      if not (found) then
-        return error("Invalid file path: " .. tostring(path))
-      end
-    end)
   end
+  return iter, _files, 0
 end
 local line_counter = re.compile([[    lines <- {| line (%nl line)* |}
     line <- {} (!%nl .)*
 ]], {
   nl = lpeg.P("\r") ^ -1 * lpeg.P("\n")
 })
-local get_lines = re.compile([[    lines <- {| line (%nl line)* |}
-    line <- {[^%nl]*}
-]], {
-  nl = lpeg.P("\r") ^ -1 * lpeg.P("\n")
-})
 local _LINE_STARTS = { }
 files.get_line_starts = function(str)
   if type(str) ~= 'string' then
@@ -196,6 +190,7 @@ files.get_line_starts = function(str)
   _LINE_STARTS[str] = line_starts
   return line_starts
 end
+local log = { }
 files.get_line_number = function(str, pos)
   local line_starts = files.get_line_starts(str)
   local lo, hi = 1, #line_starts
@@ -213,6 +208,11 @@ files.get_line = function(str, line_no)
   local line_starts = files.get_line_starts(str)
   return str:sub(line_starts[line_no] or 1, (line_starts[line_no + 1] or 1) - 2)
 end
+local get_lines = re.compile([[    lines <- {| line (%nl line)* |}
+    line <- {[^%nl]*}
+]], {
+  nl = lpeg.P("\r") ^ -1 * lpeg.P("\n")
+})
 files.get_lines = function(str)
   return get_lines:match(str)
 end
diff --git a/files.moon b/files.moon
index 9ac8ca7..6f06c8c 100644
--- a/files.moon
+++ b/files.moon
@@ -28,11 +28,33 @@ files.read = (filename)->
     _FILE_CACHE[filename] = contents
     return contents
 
-iterate_single = (item, prev) -> if item == prev then nil else item
-
 -- `walk` returns an iterator over all files matching a path.
 {:match, :gsub} = string
-iterate_single = (item, prev) -> if item == prev then nil else item
+
+-- TODO: improve sanitization
+sanitize = (path)->
+    path = gsub(path,"\\","\\\\")
+    path = gsub(path,"`","")
+    path = gsub(path,'"','\\"')
+    path = gsub(path,"$","")
+    return path
+
+files.exists = (path)->
+    return true unless io.popen("ls #{sanitize(path)}")\close!
+    if package.nomsupath
+        for nomsupath in package.nomsupath\gmatch("[^;]+")
+            return true unless io.popen("ls #{nomsupath}/#{sanitize(path)}")\close!
+    return false
+
+_browse_cache = {}
+browse = (path)->
+    unless _browse_cache[path]
+        f = io.popen('find -L "'..package.nomsupath..'/'..path..'" -not -path "*/\\.*" -type f -name "*.nom"')
+        _files = {line for line in f\lines!}
+        _files = false unless f\close!
+        _browse_cache[path] = _files
+    return _browse_cache[path]
+
 ok, lfs = pcall(require, "lfs")
 if ok
     raw_file_exists = (filename)->
@@ -44,82 +66,48 @@ if ok
             for nomsupath in package.nomsupath\gmatch("[^;]+")
                 return true if raw_file_exists(nomsupath.."/"..path)
         return false
-    -- Return 'true' if any files or directories are found, otherwise 'false', and yield every filename
-    browse = (filename)->
-        file_type, err = lfs.attributes(filename, 'mode')
-        if file_type == 'file'
-            if match(filename, "%.nom$") or match(filename, "%.lua$")
-                coroutine.yield filename
-                return true
-        elseif file_type == 'directory' or file_type == 'link'
-            for subfile in lfs.dir(filename)
-                unless subfile == "." or subfile == ".."
-                    browse(filename.."/"..subfile)
-            return true
-        elseif file_type == 'char device'
-            coroutine.yield(filename)
-            return true
 
-        return false
-    files.walk = (path)->
-        if match(path, "%.nom$") or match(path, "%.lua$") or path == 'stdin'
-            return iterate_single, path
-        return coroutine.wrap ->
-            if not browse(path) and package.nomsupath
-                for nomsupath in package.nomsupath\gmatch("[^;]+")
-                    break if browse(nomsupath.."/"..path)
-            return nil
+    export browse
+    browse = (filename)->
+        unless _browse_cache[filename]
+            _browse_cache[filename] = false
+            file_type, err = lfs.attributes(filename, 'mode')
+            if file_type == 'file'
+                if match(filename, "%.nom$") or match(filename, "%.lua$")
+                    _browse_cache[filename] = {filename}
+            elseif file_type == 'char device'
+                _browse_cache[filename] = {filename}
+            elseif file_type == 'directory' or file_type == 'link'
+                _files = {}
+                for subfile in lfs.dir(filename)
+                    unless subfile == "." or subfile == ".."
+                        for f in *(browse(filename.."/"..subfile) or {})
+                            _files[#_files+1] = f
+                _browse_cache[filename] = _files
+        return _browse_cache[filename]
 else
     if io.popen('find . -maxdepth 0')\close!
         error "Could not find 'luafilesystem' module and couldn't run system command `find` (this might happen on Windows). Please install `luafilesystem` (which can be found at: http://keplerproject.github.io/luafilesystem/ or `luarocks install luafilesystem`)", 0
-    
-    -- TODO: improve sanitization
-    sanitize = (path)->
-        path = gsub(path,"\\","\\\\")
-        path = gsub(path,"`","")
-        path = gsub(path,'"','\\"')
-        path = gsub(path,"$","")
-        return path
 
-    files.exists = (path)->
-        return true unless io.popen("ls #{sanitize(path)}")\close!
-        if package.nomsupath
-            for nomsupath in package.nomsupath\gmatch("[^;]+")
-                return true unless io.popen("ls #{nomsupath}/#{sanitize(path)}")\close!
-        return false
-
-    files.walk = (path)->
-        if match(path, "%.nom$") or match(path, "%.lua$") or path == 'stdin'
-            return iterate_single, path
-        path = sanitize(path)
-        return coroutine.wrap ->
-            f = io.popen('find -L "'..path..'" -not -path "*/\\.*" -type f -name "*.nom"')
-            found = false
-            for line in f\lines!
-                found = true
-                coroutine.yield(line)
-            if not found and package.nomsupath
-                f\close!
-                for nomsupath in package.nomsupath\gmatch("[^;]+")
-                    f = io.popen('find -L "'..package.nomsupath..'/'..path..'" -not -path "*/\\.*" -type f -name "*.nom"')
-                    for line in f\lines!
-                        found = true
-                        coroutine.yield(line)
-                    f\close!
-                    break if found
-            unless found
-                error("Invalid file path: "..tostring(path))
+files.walk = (path, flush_cache=false)->
+    if flush_cache
+        export _browse_cache
+        _browse_cache = {}
+    _files = browse(path)
+    if package.nomsupath and not _files
+        for nomsupath in package.nomsupath\gmatch("[^;]+")
+            if _files = browse(nomsupath.."/"..path) then break
+    iter = (_files, i)->
+        i += 1
+        if f = _files[i]
+            return i, f
+    return iter, _files, 0
 
 line_counter = re.compile([[
     lines <- {| line (%nl line)* |}
     line <- {} (!%nl .)*
 ]], nl:lpeg.P("\r")^-1 * lpeg.P("\n"))
 
-get_lines = re.compile([[
-    lines <- {| line (%nl line)* |}
-    line <- {[^%nl]*}
-]], nl:lpeg.P("\r")^-1 * lpeg.P("\n"))
-
 -- LINE_STARTS is a mapping from strings to a table that maps line number to character positions
 _LINE_STARTS = {}
 files.get_line_starts = (str)->
@@ -131,6 +119,7 @@ files.get_line_starts = (str)->
     _LINE_STARTS[str] = line_starts
     return line_starts
 
+log = {}
 files.get_line_number = (str, pos)->
     line_starts = files.get_line_starts(str)
     -- Binary search for line number of position
@@ -146,6 +135,11 @@ files.get_line = (str, line_no)->
     line_starts = files.get_line_starts(str)
     return str\sub(line_starts[line_no] or 1, (line_starts[line_no+1] or 1) - 2)
 
+get_lines = re.compile([[
+    lines <- {| line (%nl line)* |}
+    line <- {[^%nl]*}
+]], nl:lpeg.P("\r")^-1 * lpeg.P("\n"))
+
 files.get_lines = (str)-> get_lines\match(str)
 
 return files
diff --git a/lib/os.nom b/lib/os.nom
index 329a77f..1be7a7e 100644
--- a/lib/os.nom
+++ b/lib/os.nom
@@ -6,7 +6,7 @@ use "core"
 
 action [path of Nomsu file %filename]
     lua> ".."
-        for f in files.walk(\%filename) do return f end
+        for i,f in files.walk(\%filename) do return f end
     barf "Could not find file: \%filename"
 
 action [sh> %cmd]
@@ -21,7 +21,7 @@ action [read file %filename]
 
 compile [for file %f in %path %body] to
     Lua ".."
-        for \(%f as lua expr) in files.walk(\(%path as lua expr)) do
+        for i,\(%f as lua expr) in files.walk(\(%path as lua expr)) do
             \(%body as lua statements)
             \(compile as: === next %f ===)
         end
@@ -31,7 +31,7 @@ compile [%expr for file %f in %path] to
     Lua value ".."
         (function()
             local ret = list{}
-            for \(%f as lua expr) in files.walk(\(%path as lua expr)) do
+            for i,\(%f as lua expr) in files.walk(\(%path as lua expr)) do
                 ret[#ret+1] = \(%expr as lua statements)
             end
             return ret
diff --git a/nomsu.lua b/nomsu.lua
index 0f22eff..3ca85b5 100644
--- a/nomsu.lua
+++ b/nomsu.lua
@@ -144,7 +144,7 @@ run = function()
     if not (files.exists(f)) then
       error("Could not find: " .. tostring(f))
     end
-    for filename in files.walk(f) do
+    for _, filename in files.walk(f) do
       input_files[filename] = true
     end
   end
@@ -228,7 +228,7 @@ run = function()
   local parse_errs = { }
   for _index_0 = 1, #file_queue do
     local f = file_queue[_index_0]
-    for filename in files.walk(f) do
+    for _, filename in files.walk(f) do
       local _continue_0 = false
       repeat
         if not (filename == "stdin" or filename:match("%.nom$")) then
@@ -323,18 +323,20 @@ say ".."
     end
   end
 end
-local debugger
-if args.debugger == "nil" then
-  debugger = { }
-else
-  debugger = require(args.debugger or 'error_handling')
+do
+  local debugger
+  if args.debugger == "nil" then
+    debugger = { }
+  else
+    debugger = require(args.debugger or 'error_handling')
+  end
+  local guard
+  if type(debugger) == 'function' then
+    guard = debugger
+  else
+    guard = debugger.guard or debugger.call or debugger.wrap or debugger.run or (function(fn)
+      return fn()
+    end)
+  end
+  return guard(run)
 end
-local guard
-if type(debugger) == 'function' then
-  guard = debugger
-else
-  guard = debugger.guard or debugger.call or debugger.wrap or debugger.run or (function(fn)
-    return fn()
-  end)
-end
-return guard(run)
diff --git a/nomsu.moon b/nomsu.moon
index c2e5e05..82cdada 100755
--- a/nomsu.moon
+++ b/nomsu.moon
@@ -95,7 +95,7 @@ run = ->
     for f in *file_queue
         unless files.exists(f)
             error("Could not find: #{f}")
-        for filename in files.walk(f)
+        for _,filename in files.walk(f)
             input_files[filename] = true
 
     nomsu.can_optimize = (f)->
@@ -149,7 +149,7 @@ run = ->
 
     parse_errs = {}
     for f in *file_queue
-        for filename in files.walk(f)
+        for _,filename in files.walk(f)
             continue unless filename == "stdin" or filename\match("%.nom$")
             if args.check_syntax
                 -- Check syntax
@@ -218,8 +218,10 @@ say ".."
             elseif not ok
                 Errhand.print_error ret
 
-debugger = if args.debugger == "nil" then {}
-else require(args.debugger or 'error_handling')
-guard = if type(debugger) == 'function' then debugger
-else debugger.guard or debugger.call or debugger.wrap or debugger.run or ((fn)->fn())
-guard(run)
+
+do
+    debugger = if args.debugger == "nil" then {}
+    else require(args.debugger or 'error_handling')
+    guard = if type(debugger) == 'function' then debugger
+    else debugger.guard or debugger.call or debugger.wrap or debugger.run or ((fn)->fn())
+    guard(run)
diff --git a/nomsu_compiler.lua b/nomsu_compiler.lua
index 2d82613..ac3e741 100644
--- a/nomsu_compiler.lua
+++ b/nomsu_compiler.lua
@@ -266,7 +266,7 @@ do
     local add_bit_lua
     add_bit_lua = function(lua, bit_lua)
       local bit_leading_len = #(tostring(bit_lua):match("^[^\n]*"))
-      lua:append(lua.trailing_line_len + bit_leading_len > MAX_LINE and ",\n    " or ", ")
+      lua:append(lua:trailing_line_len() + bit_leading_len > MAX_LINE and ",\n    " or ", ")
       return lua:append(bit_lua)
     end
     local operate_on_text
@@ -334,11 +334,11 @@ do
     ["use %"] = function(self, tree, _path)
       if _path.type == 'Text' and #_path == 1 and type(_path[1]) == 'string' then
         local path = _path[1]
-        for f in files.walk(path) do
+        for _, f in files.walk(path) do
           self:run_file(f)
         end
       end
-      return LuaCode(tree.source, "for f in files.walk(", self:compile(_path), ") do nomsu:run_file(f) end")
+      return LuaCode(tree.source, "for i,f in files.walk(", self:compile(_path), ") do nomsu:run_file(f) end")
     end,
     ["test %"] = function(self, tree, _body)
       return LuaCode("")
@@ -845,7 +845,7 @@ do
               next_space = match(next_space, "[^ ]*")
             end
             nomsu:append(next_space)
-            if arg_nomsu and nomsu.trailing_line_len + #tostring(arg_nomsu) < MAX_LINE then
+            if arg_nomsu and nomsu:trailing_line_len() + #tostring(arg_nomsu) < MAX_LINE then
               if bit.type == "Block" then
                 nomsu:append(arg_nomsu)
                 next_space = "\n.."
@@ -867,7 +867,7 @@ do
             end
             pos = bit.source.stop
           end
-          if next_space == " " and nomsu.trailing_line_len > MAX_LINE then
+          if next_space == " " and nomsu:trailing_line_len() > MAX_LINE then
             next_space = "\n.."
           end
         end
@@ -1035,8 +1035,8 @@ do
           if item.type == "Block" then
             item_nomsu:parenthesize()
           end
-          if nomsu.trailing_line_len + #tostring(item_nomsu) <= MAX_LINE then
-            if nomsu.trailing_line_len > 0 then
+          if nomsu:trailing_line_len() + #tostring(item_nomsu) <= MAX_LINE then
+            if nomsu:trailing_line_len() > 0 then
               nomsu:append(", ")
             end
             nomsu:append(item_nomsu)
@@ -1053,7 +1053,7 @@ do
                 nomsu:append("\n")
               end
             else
-              if nomsu.trailing_line_len > 0 then
+              if nomsu:trailing_line_len() > 0 then
                 nomsu:append('\n')
               end
               nomsu:append(pop_comments(item.source.start), item_nomsu)
@@ -1092,8 +1092,8 @@ do
           if item.type == "Block" then
             item_nomsu:parenthesize()
           end
-          if nomsu.trailing_line_len + #tostring(item_nomsu) <= MAX_LINE then
-            if nomsu.trailing_line_len > 0 then
+          if nomsu:trailing_line_len() + #tostring(item_nomsu) <= MAX_LINE then
+            if nomsu:trailing_line_len() > 0 then
               nomsu:append(", ")
             end
             nomsu:append(item_nomsu)
@@ -1110,7 +1110,7 @@ do
                 nomsu:append("\n")
               end
             else
-              if nomsu.trailing_line_len > 0 then
+              if nomsu:trailing_line_len() > 0 then
                 nomsu:append('\n')
               end
               nomsu:append(pop_comments(item.source.start), item_nomsu)
diff --git a/nomsu_compiler.moon b/nomsu_compiler.moon
index 9ba014a..877de6b 100644
--- a/nomsu_compiler.moon
+++ b/nomsu_compiler.moon
@@ -162,7 +162,7 @@ with NomsuCompiler
             return LuaCode.Value(code.source, cls_str, repr(tostring(code.source)), ", ", @compile(code), ")")
         add_bit_lua = (lua, bit_lua)->
             bit_leading_len = #(tostring(bit_lua)\match("^[^\n]*"))
-            lua\append(lua.trailing_line_len + bit_leading_len > MAX_LINE and ",\n    " or ", ")
+            lua\append(lua\trailing_line_len! + bit_leading_len > MAX_LINE and ",\n    " or ", ")
             lua\append(bit_lua)
         operate_on_text = (text)->
             lua = LuaCode.Value(text.source, cls_str, repr(tostring(text.source)))
@@ -217,9 +217,9 @@ with NomsuCompiler
         ["use %"]: (tree, _path)=>
             if _path.type == 'Text' and #_path == 1 and type(_path[1]) == 'string'
                 path = _path[1]
-                for f in files.walk(path)
+                for _,f in files.walk(path)
                     @run_file(f)
-            return LuaCode(tree.source, "for f in files.walk(", @compile(_path), ") do nomsu:run_file(f) end")
+            return LuaCode(tree.source, "for i,f in files.walk(", @compile(_path), ") do nomsu:run_file(f) end")
 
         ["test %"]: (tree, _body)=>
             return LuaCode ""
@@ -549,7 +549,7 @@ with NomsuCompiler
                             else assert recurse(bit,inline:true)
                             next_space = match(next_space, "[^ ]*") if bit.type == "Block"
                             nomsu\append next_space
-                            if arg_nomsu and nomsu.trailing_line_len + #tostring(arg_nomsu) < MAX_LINE
+                            if arg_nomsu and nomsu\trailing_line_len! + #tostring(arg_nomsu) < MAX_LINE
                                 if bit.type == "Block"
                                     nomsu\append arg_nomsu
                                     next_space = "\n.."
@@ -567,7 +567,7 @@ with NomsuCompiler
                                 next_space = "\n.."
                             pos = bit.source.stop
 
-                        if next_space == " " and nomsu.trailing_line_len > MAX_LINE
+                        if next_space == " " and nomsu\trailing_line_len! > MAX_LINE
                             next_space = "\n.."
                     nomsu\append pop_comments(pos, '\n')
                     return nomsu
@@ -681,8 +681,8 @@ with NomsuCompiler
                     for i, item in ipairs tree
                         item_nomsu = assert recurse(item, inline:true)
                         item_nomsu\parenthesize! if item.type == "Block"
-                        if nomsu.trailing_line_len + #tostring(item_nomsu) <= MAX_LINE
-                            nomsu\append ", " if nomsu.trailing_line_len > 0
+                        if nomsu\trailing_line_len! + #tostring(item_nomsu) <= MAX_LINE
+                            nomsu\append ", " if nomsu\trailing_line_len! > 0
                             nomsu\append item_nomsu
                         else
                             if #tostring(item_nomsu) > MAX_LINE
@@ -694,7 +694,7 @@ with NomsuCompiler
                                         nomsu\append "(..)\n    ", item_nomsu
                                 nomsu\append "\n" if i < #tree
                             else
-                                nomsu\append '\n' if nomsu.trailing_line_len > 0
+                                nomsu\append '\n' if nomsu\trailing_line_len! > 0
                                 nomsu\append pop_comments(item.source.start), item_nomsu
                     nomsu\append pop_comments(tree.source.stop, '\n')
                     return NomsuCode(tree.source, "[..]\n    ", nomsu)
@@ -716,8 +716,8 @@ with NomsuCompiler
                     for i, item in ipairs tree
                         item_nomsu = assert recurse(item, inline:true)
                         item_nomsu\parenthesize! if item.type == "Block"
-                        if nomsu.trailing_line_len + #tostring(item_nomsu) <= MAX_LINE
-                            nomsu\append ", " if nomsu.trailing_line_len > 0
+                        if nomsu\trailing_line_len! + #tostring(item_nomsu) <= MAX_LINE
+                            nomsu\append ", " if nomsu\trailing_line_len! > 0
                             nomsu\append item_nomsu
                         else
                             if #tostring(item_nomsu) > MAX_LINE
@@ -729,7 +729,7 @@ with NomsuCompiler
                                         nomsu\append "(..)\n    ", item_nomsu
                                 nomsu\append "\n" if i < #tree
                             else
-                                nomsu\append '\n' if nomsu.trailing_line_len > 0
+                                nomsu\append '\n' if nomsu\trailing_line_len! > 0
                                 nomsu\append pop_comments(item.source.start), item_nomsu
                     nomsu\append pop_comments(tree.source.stop, '\n')
                     return NomsuCode(tree.source, "{..}\n    ", nomsu)