Call server-side Haskell from client browsers over Websockets.
Or: Let your browsers talk to a backend, the awesomely safe way.
On the server:
sum_rpc :: Int -> Int -> NowHs () Int
sum_rpc a b = return (a + b)In the browser:
var server = new NowHs("localhost", 8888, function () {
server.sum_rpc(1, 2, function(res) { console.log(res); });
});The remote function call is "as typesafe as Javascript allows":
Calling server.sum_rpc("1", 2, ...) will result in an error message like
Mismatching types: sum_rpc: Argument 0 was 'String', expected 'Int'
Note that this type check is done in Javascript, based on schemas auto-generated from the function's type signature, and can also be used manually, e.g. for user input validation.
When you've worked on browser-server-interfaces before, e.g. in Python or Node.js, this might be the thing for you.
NowHs can automatically convert your custom data types to JSON.
data User = User { name :: String, age :: Int }
$(deriveJSON id ''User)
$(deriveSchema ''User)
authenticated_rpc :: User -> NowHs () Bool
authenticated_rpc user = return $ age user >= 18
firstUser_rpc :: NowHs () User
firstUser_rpc = return $ User { name = "John", age = 17 }