Initial cell restrictions and url print.

src/square.rs

@@ -0,0 +1,32 @@
+use bitmaps::Bitmap;
+
+#[derive(Clone, Debug)]
+pub enum Square {
+    Value(u8),
+    Options(Bitmap<9>),
+}
+
+impl Square {
+    pub fn from_char(c: char) -> Square {
+        match c {
+            '1' => Square::Value(1),
+            '2' => Square::Value(2),
+            '3' => Square::Value(3),
+            '4' => Square::Value(4),
+            '5' => Square::Value(5),
+            '6' => Square::Value(6),
+            '7' => Square::Value(7),
+            '8' => Square::Value(8),
+            '9' => Square::Value(9),
+            '.' => Square::Options(Bitmap::mask(9)),
+            _ => panic!("Unexpected character in input: {}", c),
+        }
+    }
+
+    pub fn to_str(&self) -> String {
+        match self {
+            Square::Options(_) => " ".to_string(),
+            Square::Value(v) => v.to_string(),
+        }
+    }
+}