Thursday, May 22, 2008


I've just read Martin Fowler's article ParserFear. So, Why Not a Parser for a DSL?
Martin didn't quite specified why we need a DSL:
- Is it for business people to specify their requirements?
- Is it just 'readable' code, for programmers ?
I assume that in both cases we are trying to solve a customer's problem, by building an easy to maintain.

Let's say we use XML. Well that is a bad idea, and Martin knows it: XML is not the answer. It is not even the question. And to write XML is a difficult thing to sell, to a business-man.

Let's say that we go the ANTLR way. Which means from all the languages which are out there, none fits our needs, so we have to build our own. Ok, let's say we've build one. But now we need for our users an editor. We might need good error messages, syntax highlight, the possibility to reuse blocks of code from our programming language. Later we will need to extend our language, without hurting the users. And on the other side, the code generated will be difficult to maintain or to build abstractions on it. That's because code generation is just a raw, automatic, copy-paste machine: it doesn't build any higher-order abstractions. And the direction seems to be wrong: instead of helping our customer, we are baby-sitting our language/editor/infrastructure.

Or we go with embedded DSLs: some languages are better then others. And some languages can be easily integrated with others. Some have heavier syntax making more difficult to create a clean DSL, some are more lightweight, making a perfect match for DSLs.

Or we can go with a 'building material', a 'programmable programming language', or something similar.

Why do people fear of learning of a new language, but they invest uncountable hours in building sand-castles. Even Martin agrees: be a polyglot.

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