Mercurial > urweb
changeset 416:679b2fbbd4d0
Counter demo
| author | Adam Chlipala <adamc@hcoop.net> |
|---|---|
| date | Thu, 23 Oct 2008 11:59:48 -0400 |
| parents | 777317e8b2ae |
| children | e0e9e9eca1cb |
| files | demo/counter.ur demo/counter.urp demo/counter.urs demo/prose |
| diffstat | 4 files changed, 16 insertions(+), 2 deletions(-) [+] |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/demo/counter.ur Thu Oct 23 11:59:48 2008 -0400 @@ -0,0 +1,7 @@ +fun counter n = return <xml><body> + Current counter: {[n]}<br/> + <a link={counter (n + 1)}>Increment</a><br/> + <a link={counter (n - 1)}>Decrement</a> +</body></xml> + +fun main () = counter 0
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/demo/counter.urp Thu Oct 23 11:59:48 2008 -0400 @@ -0,0 +1,2 @@ + +counter
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/demo/counter.urs Thu Oct 23 11:59:48 2008 -0400 @@ -0,0 +1,1 @@ +val main : unit -> transaction page
--- a/demo/prose Thu Oct 23 11:38:31 2008 -0400 +++ b/demo/prose Thu Oct 23 11:59:48 2008 -0400 @@ -44,12 +44,16 @@ <p>Crafting webs of interlinked pages is easy, using recursion.</p> +counter.urp + +<p>It is also easy to pass state around via functions, in the style commonly associated with "continuation-based" web servers. As is usual for such systems, all state is stored on the client side. In this case, it is encoded in URLs.</p> + +<p>In the implementation of <tt>Counter.counter</tt>, we see the notation <tt>{[...]}</tt>, which uses type classes to inject values of different types (<tt>int</tt> in this case) into XML. It's probably worth stating explicitly that XML fragments <i>are not strings</i>, so that the type-checker will enforce that our final piece of XML is valid.</p> + form.urp <p>Here we see a basic form. The type system tracks which form inputs we include, and it enforces that the form handler function expects a record containing exactly those fields, with exactly the proper types.</p> -<p>In the implementation of <tt>handler</tt>, we see the notation <tt>{[...]}</tt>, which uses type classes to inject values of different types (<tt>string</tt> and <tt>bool</tt> in this case) into XML. It's probably worth stating explicitly that XML fragments <i>are not strings</i>, so that the type-checker will enforce that our final piece of XML is valid.</p> - listShop.urp <p>This example shows off algebraic datatypes, parametric polymorphism, and functors.</p>