diff --git a/compiler/scanner.sml b/compiler/scanner.sml
new file mode 100644
index 0000000..1eff882
--- /dev/null
+++ b/compiler/scanner.sml
@@ -0,0 +1,28 @@
+structure Scanner =
+struct
+  structure Dfa = CaseSesitiveDfa
+
+  val intDfa = Dfa.fromString "[0-9]+"
+  val wordDfa = Dfa.fromString "0w[0-9]+"
+  val realDfa = "[0-9]+.[0-9]+"
+  val idDfa = Dfa.fromString "[a-zA-Z][a-zA-Z0-9_']*"
+
+  fun helpExtractString (pos, str, acc) =
+    if pos >= String.size str then
+      raise Fail ("unterminated string: [" ^ acc ^ "]\n")
+    else
+      case String.sub (str, pos) of
+        #"\"" => (pos + 1, acc)
+      | #"\\" => 
+          if pos + 1 >= String.size str then
+            raise Fail ("unterminated string: [" ^ acc ^ "\\]\n")
+          else
+            (
+            case String.sub (str, pos + 1) of
+
+            )
+      | chr =>
+          helpExtractString (pos + 1, str, acc ^ String.implode [chr])
+
+  fun extractString (pos, str) = helpExtractString (pos. str, "")
+end
diff --git a/compiler/uses.sml b/compiler/uses.sml
new file mode 100644
index 0000000..ea7a5e2
--- /dev/null
+++ b/compiler/uses.sml
@@ -0,0 +1 @@
+use "../dfa-gen/dfa-gen.sml";