progress adding scanner

compiler/scanner.sml

@@ -1,28 +1,58 @@
 structure Scanner =
 struct
-  structure Dfa = CaseSesitiveDfa
+  structure Dfa = CaseSensitiveDfa
 
   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 skipFormattingChars (str, pos) =
+    if pos = String.size str then
+      raise Fail "unterminated formatting char sequence"
+    else
+      let
+        val chr = String.sub (str, pos)
+      in
+        if Char.isSpace chr then skipFormattingChars (str, pos + 1)
+        else if chr = #"\\" then pos + 1
+        else raise Fail "encountered non-space char in formatting sequence"
+      end
+
+  fun getEscapeChr (str, pos, acc) =
+    case String.sub (str, pos) of
+      #"a" => (pos + 1, acc ^ "\a")
+    | #"b" => (pos + 1, acc ^ "\b")
+    | #"t" => (pos + 1, acc ^ "\t")
+    | #"n" => (pos + 1, acc ^ "\n")
+    | #"v" => (pos + 1, acc ^ "\v")
+    | #"f" => (pos + 1, acc ^ "\f")
+    | #"r" => (pos + 1, acc ^ "\r")
+    | #"\"" => (pos + 1, acc ^ "\"")
+    | #"\\" => (pos + 1, acc ^ "\\")
+    | chr =>
+        if Char.isSpace chr then
+          (* formatting characters ahead *)
+          let val nextPos = skipFormattingChars (str, pos + 1)
+          in (nextPos, acc)
+          end
+        else
+          raise Fail "invalid escape char"
+
   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
+            let val (nextPos, acc) = getEscapeChr (str, pos + 1, acc)
+            in helpExtractString (nextPos, str, acc)
+            end
+      | chr => helpExtractString (pos + 1, str, acc ^ String.implode [chr])
 
-            )
-      | chr =>
-          helpExtractString (pos + 1, str, acc ^ String.implode [chr])
-
-  fun extractString (pos, str) = helpExtractString (pos. str, "")
+  fun extractString (pos, str) = helpExtractString (pos, str, "")
 end