Add hints

Author: ceddlyburge

concepts/web-applications-1/about.md

@@ -16,6 +16,7 @@ type alias Model =
 
 `update` is a function that gets called with a `Msg` when there's a change (like the user clicking a button).
 It takes the current `Model` and the `Msg`, and returns a new `Model`.
+The `Msg` can be any type, but in any useful application it is always a [custom type][custom-type].
 
 ```elm
 type Msg
@@ -78,6 +79,7 @@ init =
 ```
 
 [record]: https://elm-lang.org/docs/records
+[custom-type]: https://guide.elm-lang.org/types/custom_types.html
 [elm-guide-text-fields]: https://guide.elm-lang.org/architecture/text_fields
 [html-elements]: https://package.elm-lang.org/packages/elm/html/latest/Html
 [element-attributes]: https://package.elm-lang.org/packages/elm/html/latest/Html-Attributes

exercises/concept/paulas-palindromes/.docs/hints.md

@@ -0,0 +1,44 @@
+# Hints
+
+## General
+
+- Check out the [Elm Guide][elm-guide], which has a nice worked example that is similar.
+
+## 1. Define the Model type for the application
+
+- The `Model` contains the application's state - all the data that the application needs.
+- This application just needs a string to store the text in the Text Box.
+- It can be any type, but in any useful application it is always a [record][record].
+
+## 2. Define the Msg type for the application
+
+- The `Msg` type is a defines the messages that are passed to the `update` function, to trigger specific changes in the model.
+- This application only needs one change to the model - updating the model when the text in the Text Box changes.
+- It can be any type, but in any useful application it is always a [custom type][custom-type].
+
+## 3. Write the update function
+
+- In any useful application the update function will use a `case` statement to pattern match on the `Msg` parameter.
+- IN each branch of the case statement it will extract information it needs from the `Msg` parameter and return an updated `Model`
+- The `Model` should be a record, and [record update syntax][record-update-syntax] is normally used.
+
+## 4. Write the view function
+
+- The `view` function should probably return a `div` for the root element
+- The first child should be an `input`, with a `value` attribute for the current text, and an `nInput` attribute / event with the relevant variant of the `Msg`.
+- The second child should probably be another `div` with a `text`child stating whether the text is a palindrome or not.
+
+## 5. Write the init function
+
+- This should simply return a `Model` with sensible default values (probably an empty string).
+
+## 6. Write the main function
+
+- The main function should just called [`Browser.sandbox`][browser-sandbox]
+- `Browser.sandbox` requires a [record][record] argument with the `init`, `update` and `view` functions.
+
+[elm-guide]: https://guide.elm-lang.org/architecture/text_fields
+[record]: https://elm-lang.org/docs/records
+[custom-type]: https://guide.elm-lang.org/types/custom_types.html
+[record-update-syntax]: https://elm-lang.org/docs/records#updating-records
+[browser-sandbox]: https://package.elm-lang.org/packages/elm/browser/latest/Browser#sandbox

exercises/concept/paulas-palindromes/.docs/instructions.md

@@ -30,11 +30,11 @@ Inside this root element, there should be an `input` element (the Text Box),and
 
 ## 5. Write the init function
 
-The `init` function should return a sensible initial `Model` value .
+The `init` function should return a sensible initial `Model` value.
 
 ## 6. Write the main function
 
-The `main` function should call [`Browser.sandbox`][browser-sandbox], passing aa record parameter with the `init`, `update` and `view` functions.
+The `main` function should call [`Browser.sandbox`][browser-sandbox], passing a record parameter with the `init`, `update` and `view` functions.
 
 [palindrome-crossword-clues]: https://www.theguardian.com/crosswords/crossword-blog/2012/nov/01/cryptic-crosswords-beginners-palindromes
 [browser-sandbox]: https://package.elm-lang.org/packages/elm/browser/latest/Browser#sandbox