expand example

Author: stoeffel

README.md

@@ -35,8 +35,31 @@ So you define `VerifiedModel` like this:
 and you can verify this by using a `Json.Decode.Pipeline`-like api.
 
 ```elm
-     Verify.ok VerifiedModel
-         |> keep .id
-         |> verify .firstName (Maybe.Verify.isJust "error")
-         |> verify .lastName (Maybe.Verify.isJust"error")
+     validator : Validator String Model VerifiedModel
+     validator =
+        Verify.ok VerifiedModel
+            |> keep .id
+            |> verify .firstName (Maybe.Verify.isJust "no first name")
+            |> verify .lastName (Maybe.Verify.isJust"no last name")
+```
+
+You can execute a `Validator` just by calling it.
+
+```elm
+    validator { id = 1, firstName = Just "Luke", lastName = Just "Skywalker" }
+    --> Ok { id = 1, firstName = "Luke", lastName = "Skywalker" }
+
+    validator { id = 1, firstName = Nothing, lastName = Nothing }
+    --> Err [ "no first name", "no last name" ]
+```
+
+So far we've used `Validator`s from `Maybe.Verify`. There are other `Validator`s in this package, but it's also simple to write your own `Validator`.
+
+```elm
+  possitiveNumber : error -> Validator error Int Int
+  possitiveNumber error input =
+    if input >= 0 then
+       Ok input
+    else
+       Err [ error ]
 ```