Remade lets with bind & improvements

test_program

@@ -1,4 +1,41 @@
-data Maybe (a) where {
+data List (a) where {
-    Nothing : Maybe (a)
+    Nil : List (a)
-    Just : a -> Maybe (a)
+    Cons : a -> List (a) -> List (a)
-}
+};
+
+data Bool () where {
+    True : Bool ()
+    False : Bool ()
+   };
+
+-- hello_world = Cons 'h' (Cons 'e' (Cons 'l' (Cons 'l' (Cons 'o' (Cons ' ' (Cons 'w' (Cons 'o' (Cons 'r' (Cons 'l' (Cons 'd' Nil)))))))))) ;
+
+-- length : List (a) -> Int ;
+-- length xs = case xs of {
+--     Nil => 0 ;
+--     Cons x xs => length xs
+-- };
+
+-- head : List (a) -> a ;
+-- head xs = case xs of {
+--     Cons x xs => x
+-- };
+
+firstIsOne : List (Int) -> Bool () ;
+firstIsOne xs = case xs of {
+    Cons x xs => case x of {
+            1 => True ;
+            _ => case xs of {
+                    Cons x xs => False ;
+                    _ => False
+                }
+            };
+    _ => False
+    };
+
+-- firstIsOne :: [Int] -> Bool 
+-- firstIsOne xs = case xs of
+--     (1 : xs) -> True
+--     _ -> False
+
+main = firstIsOne (Cons 'a' Nil)