Saturday, October 21, 2006

ErlTL 0.9.1

In the past couple of days, I've done a lot of ErlTL hacking. Here's what I've accomplished:

- I added support full Erlang function declarations. ErlTL now gives you unlimited flexibilty in function declarations. You can decide what the variables are, add guards, and use Erlang's full pattern matching capabilities. With pattern matching, your don't have to rely as much on cumbersome if-else statements. Here's a sample function declaration that's now legal in ErlTL:

<%@ foo(Bar, {Baz, Boing} = Data) when is_integer(Bar) %>

- I added support for top-level declarations. At the top of your template file, you can now declare Erlang module attributes, compiler directives, and even complete functions (although the latter is not advised as template files aren't meant to contain logic that's better put in a regular Erlang module). One of main benefits is that now you call functions from other templates with less code by importing them. The new syntax for top-level declarations is '<%~ .. %>'. Here's an example:

-author("Yariv Sadan").
[foo/1, bar/1, baz/2]).

%% this is allowed, but not advised
pluralize(Noun) -> [Noun, "s"].
<% foo(Data) %>

- I fixed a bug that caused ErlTL to fail to parse multi-line Erlang expressions.
- I rewrote almost all the code. Yes, the last code worked, but it needed to be prettier :)

And finally, here's an example of a complete ErlTL 0.9.1 template:

%% date: 10/21/2006
-author("Yariv Sadan").
-import(widgets, [foo/1, bar/2, baz/3]).
This is a sample ErlTL template that renders a
list of albums in HTML

<% [album(A) || A <- Data] %>

<%@ album({Title, Artist, Songs}) %>
Title: <% Title %>
Artist: <% Artist %>

<% [song(Number, Name) || {Number, Name} <- Songs] %>

<%@ song(Number, Name) when size(Name) > 15 %>
<%? <> = Name %>
<% song(Number, [First, <<"...">>]) %>

<%@ song(Number, Name) %>
Class =
case Number rem 2 of
0 -> <<"even">>;
1 -> <<"odd">>

<% integer_to_list(Number) %>
<% Name %>

Damn -- now I really can't wait to build those killer Erlang webapps! :)

1 comment:

Francisco said...

Hi Yariv,
I find your solution interesting and with lots of promise, and I will certainly spend some time learning this; though I do have a question: I am an Erlang newbie and have some experience with Django, could there be an easy way to allow natively the use of other template engines besides ErlTL (like erlang/django ErlyDTL)?
Thanks and keep up the god work.