You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
283 lines
9.2 KiB
HTML
283 lines
9.2 KiB
HTML
9 years ago
|
<!doctype html>
|
||
|
|
|
||
|
|
<title>CodeMirror: Haskell-literate mode</title>
|
||
|
|
<meta charset="utf-8"/>
|
||
|
|
<link rel=stylesheet href="../../doc/docs.css">
|
||
|
|
|
||
|
|
<link rel="stylesheet" href="../../lib/codemirror.css">
|
||
|
|
<script src="../../lib/codemirror.js"></script>
|
||
|
|
<script src="haskell-literate.js"></script>
|
||
|
|
<script src="../haskell/haskell.js"></script>
|
||
|
|
<style>.CodeMirror {
|
||
|
|
border-top : 1px solid #DDDDDD;
|
||
|
|
border-bottom : 1px solid #DDDDDD;
|
||
|
|
}</style>
|
||
|
|
<div id=nav>
|
||
|
|
<a href="http://codemirror.net"><h1>CodeMirror</h1><img id=logo
|
||
|
|
src="../../doc/logo.png"></a>
|
||
|
|
|
||
|
|
<ul>
|
||
|
|
<li><a href="../../index.html">Home</a>
|
||
|
|
<li><a href="../../doc/manual.html">Manual</a>
|
||
|
|
<li><a href="https://github.com/codemirror/codemirror">Code</a>
|
||
|
|
</ul>
|
||
|
|
<ul>
|
||
|
|
<li><a href="../index.html">Language modes</a>
|
||
|
|
<li><a class=active href="#">Haskell-literate</a>
|
||
|
|
</ul>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<article>
|
||
|
|
<h2>Haskell literate mode</h2>
|
||
|
|
<form>
|
||
|
|
<textarea id="code" name="code">
|
||
|
|
> {-# LANGUAGE OverloadedStrings #-}
|
||
|
|
> {-# OPTIONS_GHC -fno-warn-unused-do-bind #-}
|
||
|
|
> import Control.Applicative ((<$>), (<*>))
|
||
|
|
> import Data.Maybe (isJust)
|
||
|
|
|
||
|
|
> import Data.Text (Text)
|
||
|
|
> import Text.Blaze ((!))
|
||
|
|
> import qualified Data.Text as T
|
||
|
|
> import qualified Happstack.Server as Happstack
|
||
|
|
> import qualified Text.Blaze.Html5 as H
|
||
|
|
> import qualified Text.Blaze.Html5.Attributes as A
|
||
|
|
|
||
|
|
> import Text.Digestive
|
||
|
|
> import Text.Digestive.Blaze.Html5
|
||
|
|
> import Text.Digestive.Happstack
|
||
|
|
> import Text.Digestive.Util
|
||
|
|
|
||
|
|
Simple forms and validation
|
||
|
|
---------------------------
|
||
|
|
|
||
|
|
Let's start by creating a very simple datatype to represent a user:
|
||
|
|
|
||
|
|
> data User = User
|
||
|
|
> { userName :: Text
|
||
|
|
> , userMail :: Text
|
||
|
|
> } deriving (Show)
|
||
|
|
|
||
|
|
And dive in immediately to create a `Form` for a user. The `Form v m a` type
|
||
|
|
has three parameters:
|
||
|
|
|
||
|
|
- `v`: the type for messages and errors (usually a `String`-like type, `Text` in
|
||
|
|
this case);
|
||
|
|
- `m`: the monad we are operating in, not specified here;
|
||
|
|
- `a`: the return type of the `Form`, in this case, this is obviously `User`.
|
||
|
|
|
||
|
|
> userForm :: Monad m => Form Text m User
|
||
|
|
|
||
|
|
We create forms by using the `Applicative` interface. A few form types are
|
||
|
|
provided in the `Text.Digestive.Form` module, such as `text`, `string`,
|
||
|
|
`bool`...
|
||
|
|
|
||
|
|
In the `digestive-functors` library, the developer is required to label each
|
||
|
|
field using the `.:` operator. This might look like a bit of a burden, but it
|
||
|
|
allows you to do some really useful stuff, like separating the `Form` from the
|
||
|
|
actual HTML layout.
|
||
|
|
|
||
|
|
> userForm = User
|
||
|
|
> <$> "name" .: text Nothing
|
||
|
|
> <*> "mail" .: check "Not a valid email address" checkEmail (text Nothing)
|
||
|
|
|
||
|
|
The `check` function enables you to validate the result of a form. For example,
|
||
|
|
we can validate the email address with a really naive `checkEmail` function.
|
||
|
|
|
||
|
|
> checkEmail :: Text -> Bool
|
||
|
|
> checkEmail = isJust . T.find (== '@')
|
||
|
|
|
||
|
|
More validation
|
||
|
|
---------------
|
||
|
|
|
||
|
|
For our example, we also want descriptions of Haskell libraries, and in order to
|
||
|
|
do that, we need package versions...
|
||
|
|
|
||
|
|
> type Version = [Int]
|
||
|
|
|
||
|
|
We want to let the user input a version number such as `0.1.0.0`. This means we
|
||
|
|
need to validate if the input `Text` is of this form, and then we need to parse
|
||
|
|
it to a `Version` type. Fortunately, we can do this in a single function:
|
||
|
|
`validate` allows conversion between values, which can optionally fail.
|
||
|
|
|
||
|
|
`readMaybe :: Read a => String -> Maybe a` is a utility function imported from
|
||
|
|
`Text.Digestive.Util`.
|
||
|
|
|
||
|
|
> validateVersion :: Text -> Result Text Version
|
||
|
|
> validateVersion = maybe (Error "Cannot parse version") Success .
|
||
|
|
> mapM (readMaybe . T.unpack) . T.split (== '.')
|
||
|
|
|
||
|
|
A quick test in GHCi:
|
||
|
|
|
||
|
|
ghci> validateVersion (T.pack "0.3.2.1")
|
||
|
|
Success [0,3,2,1]
|
||
|
|
ghci> validateVersion (T.pack "0.oops")
|
||
|
|
Error "Cannot parse version"
|
||
|
|
|
||
|
|
It works! This means we can now easily add a `Package` type and a `Form` for it:
|
||
|
|
|
||
|
|
> data Category = Web | Text | Math
|
||
|
|
> deriving (Bounded, Enum, Eq, Show)
|
||
|
|
|
||
|
|
> data Package = Package Text Version Category
|
||
|
|
> deriving (Show)
|
||
|
|
|
||
|
|
> packageForm :: Monad m => Form Text m Package
|
||
|
|
> packageForm = Package
|
||
|
|
> <$> "name" .: text Nothing
|
||
|
|
> <*> "version" .: validate validateVersion (text (Just "0.0.0.1"))
|
||
|
|
> <*> "category" .: choice categories Nothing
|
||
|
|
> where
|
||
|
|
> categories = [(x, T.pack (show x)) | x <- [minBound .. maxBound]]
|
||
|
|
|
||
|
|
Composing forms
|
||
|
|
---------------
|
||
|
|
|
||
|
|
A release has an author and a package. Let's use this to illustrate the
|
||
|
|
composability of the digestive-functors library: we can reuse the forms we have
|
||
|
|
written earlier on.
|
||
|
|
|
||
|
|
> data Release = Release User Package
|
||
|
|
> deriving (Show)
|
||
|
|
|
||
|
|
> releaseForm :: Monad m => Form Text m Release
|
||
|
|
> releaseForm = Release
|
||
|
|
> <$> "author" .: userForm
|
||
|
|
> <*> "package" .: packageForm
|
||
|
|
|
||
|
|
Views
|
||
|
|
-----
|
||
|
|
|
||
|
|
As mentioned before, one of the advantages of using digestive-functors is
|
||
|
|
separation of forms and their actual HTML layout. In order to do this, we have
|
||
|
|
another type, `View`.
|
||
|
|
|
||
|
|
We can get a `View` from a `Form` by supplying input. A `View` contains more
|
||
|
|
information than a `Form`, it has:
|
||
|
|
|
||
|
|
- the original form;
|
||
|
|
- the input given by the user;
|
||
|
|
- any errors that have occurred.
|
||
|
|
|
||
|
|
It is this view that we convert to HTML. For this tutorial, we use the
|
||
|
|
[blaze-html] library, and some helpers from the `digestive-functors-blaze`
|
||
|
|
library.
|
||
|
|
|
||
|
|
[blaze-html]: http://jaspervdj.be/blaze/
|
||
|
|
|
||
|
|
Let's write a view for the `User` form. As you can see, we here refer to the
|
||
|
|
different fields in the `userForm`. The `errorList` will generate a list of
|
||
|
|
errors for the `"mail"` field.
|
||
|
|
|
||
|
|
> userView :: View H.Html -> H.Html
|
||
|
|
> userView view = do
|
||
|
|
> label "name" view "Name: "
|
||
|
|
> inputText "name" view
|
||
|
|
> H.br
|
||
|
|
>
|
||
|
|
> errorList "mail" view
|
||
|
|
> label "mail" view "Email address: "
|
||
|
|
> inputText "mail" view
|
||
|
|
> H.br
|
||
|
|
|
||
|
|
Like forms, views are also composable: let's illustrate that by adding a view
|
||
|
|
for the `releaseForm`, in which we reuse `userView`. In order to do this, we
|
||
|
|
take only the parts relevant to the author from the view by using `subView`. We
|
||
|
|
can then pass the resulting view to our own `userView`.
|
||
|
|
We have no special view code for `Package`, so we can just add that to
|
||
|
|
`releaseView` as well. `childErrorList` will generate a list of errors for each
|
||
|
|
child of the specified form. In this case, this means a list of errors from
|
||
|
|
`"package.name"` and `"package.version"`. Note how we use `foo.bar` to refer to
|
||
|
|
nested forms.
|
||
|
|
|
||
|
|
> releaseView :: View H.Html -> H.Html
|
||
|
|
> releaseView view = do
|
||
|
|
> H.h2 "Author"
|
||
|
|
> userView $ subView "author" view
|
||
|
|
>
|
||
|
|
> H.h2 "Package"
|
||
|
|
> childErrorList "package" view
|
||
|
|
>
|
||
|
|
> label "package.name" view "Name: "
|
||
|
|
> inputText "package.name" view
|
||
|
|
> H.br
|
||
|
|
>
|
||
|
|
> label "package.version" view "Version: "
|
||
|
|
> inputText "package.version" view
|
||
|
|
> H.br
|
||
|
|
>
|
||
|
|
> label "package.category" view "Category: "
|
||
|
|
> inputSelect "package.category" view
|
||
|
|
> H.br
|
||
|
|
|
||
|
|
The attentive reader might have wondered what the type parameter for `View` is:
|
||
|
|
it is the `String`-like type used for e.g. error messages.
|
||
|
|
But wait! We have
|
||
|
|
releaseForm :: Monad m => Form Text m Release
|
||
|
|
releaseView :: View H.Html -> H.Html
|
||
|
|
... doesn't this mean that we need a `View Text` rather than a `View Html`? The
|
||
|
|
answer is yes -- but having `View Html` allows us to write these views more
|
||
|
|
easily with the `digestive-functors-blaze` library. Fortunately, we will be able
|
||
|
|
to fix this using the `Functor` instance of `View`.
|
||
|
|
fmap :: Monad m => (v -> w) -> View v -> View w
|
||
|
|
A backend
|
||
|
|
---------
|
||
|
|
To finish this tutorial, we need to be able to actually run this code. We need
|
||
|
|
an HTTP server for that, and we use [Happstack] for this tutorial. The
|
||
|
|
`digestive-functors-happstack` library gives about everything we need for this.
|
||
|
|
[Happstack]: http://happstack.com/
|
||
|
|
|
||
|
|
> site :: Happstack.ServerPart Happstack.Response
|
||
|
|
> site = do
|
||
|
|
> Happstack.decodeBody $ Happstack.defaultBodyPolicy "/tmp" 4096 4096 4096
|
||
|
|
> r <- runForm "test" releaseForm
|
||
|
|
> case r of
|
||
|
|
> (view, Nothing) -> do
|
||
|
|
> let view' = fmap H.toHtml view
|
||
|
|
> Happstack.ok $ Happstack.toResponse $
|
||
|
|
> template $
|
||
|
|
> form view' "/" $ do
|
||
|
|
> releaseView view'
|
||
|
|
> H.br
|
||
|
|
> inputSubmit "Submit"
|
||
|
|
> (_, Just release) -> Happstack.ok $ Happstack.toResponse $
|
||
|
|
> template $ do
|
||
|
|
> css
|
||
|
|
> H.h1 "Release received"
|
||
|
|
> H.p $ H.toHtml $ show release
|
||
|
|
>
|
||
|
|
> main :: IO ()
|
||
|
|
> main = Happstack.simpleHTTP Happstack.nullConf site
|
||
|
|
|
||
|
|
Utilities
|
||
|
|
---------
|
||
|
|
|
||
|
|
> template :: H.Html -> H.Html
|
||
|
|
> template body = H.docTypeHtml $ do
|
||
|
|
> H.head $ do
|
||
|
|
> H.title "digestive-functors tutorial"
|
||
|
|
> css
|
||
|
|
> H.body body
|
||
|
|
> css :: H.Html
|
||
|
|
> css = H.style ! A.type_ "text/css" $ do
|
||
|
|
> "label {width: 130px; float: left; clear: both}"
|
||
|
|
> "ul.digestive-functors-error-list {"
|
||
|
|
> " color: red;"
|
||
|
|
> " list-style-type: none;"
|
||
|
|
> " padding-left: 0px;"
|
||
|
|
> "}"
|
||
|
|
</textarea>
|
||
|
|
</form>
|
||
|
|
|
||
|
|
<p><strong>MIME types
|
||
|
|
defined:</strong> <code>text/x-literate-haskell</code>.</p>
|
||
|
|
|
||
|
|
<p>Parser configuration parameters recognized: <code>base</code> to
|
||
|
|
set the base mode (defaults to <code>"haskell"</code>).</p>
|
||
|
|
|
||
|
|
<script>
|
||
|
|
var editor = CodeMirror.fromTextArea(document.getElementById("code"), {mode: "haskell-literate"});
|
||
|
|
</script>
|
||
|
|
|
||
|
|
</article>
|