Libraries, some more

I think we’re getting very close to having libraries sufficiently developed that we can return to focusing on actual projects. Upcoming gem releases (tomorrow or early next week) will have a good start for building libraries and grammars. A lot of work remains, but there’s enough there that we can get real work done now.

Our current play library is the following:

In an application (assuming the ‘m’ prefix maps to ‘http://example.com/ns/grammar’), we can use the grammar rules ‘something’ and ‘something2’ as filters and constraints. We can also use them as functions for matching and parsing strings.

We also have the functions ‘m:double’ (a mapping) and ‘m:fctn’ (a regular function).

Finally, we have the action ‘m:actn’ which accepts enclosed elements as actions and returns thrice the value returned by running the actions. The ‘f:eval’ function evaluates the referenced code using the current node in the context.

In general, mappings will be called with their argument as the current node. Functions will be called with each argument as a separate variable ($1, $2, $3, …) and with $0 representing all of the arguments as one list. Reductions will be called with a long list in $0.

We still have a few more things we need to do to make these XML-based libraries as flexible as the Ruby ones, but that will come as we need that flexibility.

We also need to think about how we want to document libraries… but enough for one day.

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James

James is a software developer and self-published author. He received his B.S. in Math and Physics and his M.A. in English from Texas A&M University. After spending almost two decades in academia, he now works in the Washington, DC, start up world.