LinQ is often understood in terms of introducing a Domain Specific Language to work with data to C# and .Net in general. The fact is:it is not, and there is a considerable difference between LinQ syntax nature and a DSL. The problem is that DSL definition is blur enough to take anything interesting or cool under it!
Erik Meijer talks about less known LINQ features, like meta programming, about the differences between functional languages and OO ones, asynchronous computation, and others.
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Given the growing interest in Domain Specific Languages, Michael Feathers provides some reflections on external DSLs, their advantages and pitfalls as well as possible success and failure factors that he believes to be function of far more than the technology.
Having worked with several Object-Relational mapping frameworks in the last few years, I got to a point where I couldn’t justify their complexity in my project. We often talk about the mismatch between the database and the object worlds, and that is where ORMs are often stated and referenced for “bridging the gap”!
Well I prefer to call it lifting the gap, or highering the gap, to have it now between DAOs and the rest of the code than having it between database and code.But I wouldn’t call this in any way reducing the gap.
This is an interview I did at QCon with Ted Neward. Talking to Ted was very interesting even though arguing with him turned to be not easy at all :)
Lately I’ve been writing some programs with Haskell (a pure functional programming language) and I noticed that I am not using GoF design patterns anymore, and that got me to a question: What are GoF design patterns? And why do we need them?
This actually reminds me of a good definition I read (I can’t recall where) of these design patterns: Resolutions to programming language limitations implemented using the programming language available syntax. When one learns a programming language, he learns to express what he wants to express using a very limited set of expressions of the language. The problem with this is that his imagination in this environment gets boxed! So what are GoF design patterns?
Most of GoF design patterns are inspired from Smaltalk, so what is so special about Smaltalk? Closures! It turns out that Java and C++ didn’t have closures and higher order functions. Some of the Design Patterns came to rescue and provide "alternatives" to these powerful constructs or workarounds to resolve these limitations. Such an approach requires a kind of object gymnastics and results in an explosion of classes!
I am now on a project where I use C# 3.5 features, and guess what? Suddenly I use much less strategies, much less templates. I write much less code yet being as or even more flexible. Powerful lambda expressions!
Update: DSLs also come from fp paradigm!
There is a widespread opinion that a good DSL has to be English-like. Dave Thomas advocates against such approach asserting that DSL are not about getting as close as possible to natural languages and that having this as a guiding principle of DSL design can be rather detrimental. He also highlights what he believes is important in DSL design and provides some examples of successful DSL.
Achieving readability and expressiveness by writing English-like code is one of the trends on the rise in today’s industry. Michael Feathers advocates for considering other alternatives that can be instrumental for improving code expressiveness. He argues that in some circumstances symbolic approach is more appropriate than the narrative one and highlights some trades-offs between them.
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