Thoughts on agile software development
Not long ago, I wrote about public parameterless methods for records. Now let’s take it a step further and let a whole host of other methods run wild in our templates. The parameterless methods for records were added for the sake of symmetry. Now we’re going to expand the application with a truly new feature.
CongoCC is a modern successor to JavaCC that is undergoing continuous development. Here are two new features that Jon Revusky brought to my attention. Cardinality Constraints and Contextual Keywords.
FreshMarker has always optimised constant expressions during template parsing. The expression 2 + 3 becomes 5 before the first process(…) call is ever made. That optimisation, however, had a hard boundary: anything involving the ~~ operator, registered formatters, or context-free built-ins was left untouched because the parser had no access to the configuration that governs them. This post describes the ParseContext, a new concept that hands build-time knowledge to the template builders and what that unlocks.
While designing a new feature, I once again stumbled upon a feature of the template language that I haven’t liked for a long time. The syntax of the directives is modeled after HTML elements, not XML elements. As long as you don’t want to change the syntax of the template language, this isn’t a problem. But if you have a great idea for a new feature, you’re in for a world of trouble.
When replicating the concepts of another template engine, there are always moments when you put off working on a particular concept. This rarely has anything to do with the complexity of the concept itself, but often stems from a personal aversion. For FreshMarker, this has meant that some concepts have been implemented late or completely reworked. Some concepts are still awaiting implementation. One of these concepts is the parameters of the nested directive, which will be implemented for FreshMarker 2.7.0.
Vor vier Jahren begann das Abenteuer FreshMarker mit dem Blog-Beitrag „FreshMarker, eine frische Template Engine für Java“. Was als akademisches Experiment startete, hat sich inzwischen zu einer vielseitigen und stabilen Template Engine entwickelt. Mit Version 2.5.0 und insgesamt 87 Blog-Beiträgen, die verschiedenste Aspekte beleuchten, ist nun der richtige Zeitpunkt für ein Resümee.
If you want to interpret a programming language or a DSL, there’s no way around using a parser generator. At the heart of FreshMarker is a template parser generated by the CongoCC parser generator. I can’t praise this JavaCC successor from Jon Revusky highly enough. Many new features and completely revised parts make the parser generator much more usable than its seemingly dead predecessor. CongoCC also helps wonderfully with a small current problem.
To implement a new built-in for sequences, lambdas were added as a new language component of the FreshMarker Expression Language. The lambda expression made it much easier to map the semantics of the new count built-in in an easily readable syntax. Now that lambda expressions are available, what else can they be used for and what still needs to be implemented?
In the first article on the Select Operator, the implementation was provisionally terminated with a few weaknesses. In this article, two of the weaknesses are eliminated.
FreshMarker allows you to overload a wide variety of operators for your own model types. These operators are multiplication, addition, negation and comparison operators. For strings, the addition operator + has so far been overloaded to realize a string concatenation. In this blog post, we want to implement comparison operators for strings.