Monday, November 11, 2013

Learning from the Haskell compiler

Haskell programming is naturally one level of abstraction above other languages either functional or not. It is not the functional paradigm. It is the type inference and, specially, the category theoretical grounds in which the language is based, for which functional and imperative paradigms are particular cases.

The extra level of abstraction means that you are one level up in the tree of possibilities. For example, you can define the very meaning of a sequence of statements in a Monad Instance. That, in other languages is fixed.

That means that you have a extra level of things to learn and explore. For example I created a DSL for web applications time ago and still I´m learning my own language. Sometimes my programs type check, but they do not perform what I was expecting, But it does other interesting thing. The code was a product of my own misunderstanding or my lack of concentration, but the type checker say: its valid, let´s run it. Then I check it again and voila, when I examine the program I discover a new usage of the same elements I defined that I never though previously possible.

Sometimes the error messages tell me new instances of things that I would never though about. Some of them seem crazy, but after a second though, I find that is not as crazy as it seems but, sometimes I´m not willing to accept yet another extra level of abstraction that my compiler is suggesting as result of an error.

For beginners this flood of information is confusing,as well as for expert programmers they just want their job done, but thanks in part to this interaction I´m here talking about abstract web combinators when what I initially needed from Haskell was the fsstest way to see "hello world" in a web browser.
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