What is UrlDisp
URLs are everywhere on the web. Most of them, however, are hard to remember, because they are meaningless for humans. This is wrong, however: URLs are a part of user interface, and therefore should be kept simple, meaningful and memorizeable.
UrlDisp provides (Fast)CGI programs a minimalistic domain-specific parser for URLs.
Hierarchical part of the URL is tokenized and matched against rules defined using UrlDisp combinators. Every rule consists of, basically, a predicate and a CGI action. Once a predicate is true, an action is performed; otherwise, alternatives are tried in order. The matching algorithm is backtracking.
A regular CGI action looks like this:
output "hello, world!"
Adding a predicate:
-- if URL matches /hello, then output "hello, world!" h |/ "hello" *> output "hello, world!"
-- if URL contains /hello, output "woot, it works!", otherwise check for -- /foo (h |/ "hello" *> output "woot, it works!") <|> (h |/ "foo" *> output "foo")
As you can see, the |/ combinator matches current token against it's right operand. h is a special predicate that matches anything, it is used to begin a string of combinators.
One can also match against
- URL parameters,
- HTTP methods,
- and also convert token into a variable which is an instance of Read
There's also an API which is believed to be more human-readable.