gmap fromFoo

gmap (Foo i -> i) -- ошибка!

def (_, _, res) = lst.Aggregate( (  0,  true, List()), ((prev, skip, res), cur) =>
   if (!skip && prev + 1 == cur) (cur,  true, { res.Add(cur); res })
   else                          (cur, false, res));

- Is relational data the main reason to start LINQ development?

It is a common misconception that LINQ is strongly coupled to relational data. If you look at the various papers on my homepage (http://research.microsoft.com/en-us/um/people/emeijer/ErikMeijer.html) you see that I emphasize LINQ’s monadic roots. Monads are a way to reason about general “computations” and querying a relational database is just one possible example of that. Take Rx http://msdn.microsoft.com/en-us/devlabs/ee794896.aspx for instance, you see that we define LINQ over event-based and asynchronous computations. That is quite different from your typical relational database I would say. Other examples include LINQ to Sharepoint, LINQ to Twitter, …. Those query “data” but not relational data. Have a look at http://homepages.inf.ed.ac.uk/wadler/topics/monads.html for more examples of possible LINQ data sources.

Если выкинуть работу с реляционным источником из списка, то вся обозначенная проблема становится достаточно несущественной и незначительной, чтобы не расшибаться в лепешку ради специальной поддержки специального механизма в языке.

- "if you throw away relational data application then impedance mismatch problem becomes somewhat inessential and insignificant to put such a huge effort to add a special support into the language". Do you think it is correct?

As the answer to the first question implies, LINQ is not tied to relational data. What I am trying to say in the interview you quote is that what LINQ does is to emphasize the correspondence between different data models by defining a common interface/pattern that a “data source” can expose and then define a query language in terms of that interface. This in contrast to ther approaches where people are converting their data into a universal data model and querying on that.
LINQ is about composing computations, querying relational data is one special, and important, form of composing computations.

- What are the main advantages of LINQ over using plain simple loops when LINQ is not used for relational data interaction?

That is not a correct question since, again, you assume that you are dealing with explicit data sources. How could you use loops to do Rx-style computations?

- Do you think LINQ-like approach would be a good addition for other languages?

Well, F#, Haskell and Scala all have (monad) comprehensions, so obviously yes.

Y>З.Ы. Завтра напишу ему спасибо за ответы, так что есле есть еще вопросы, могу невзначай присовокупить к своему thank you имейлу

He runs the Cloud Programmability Team at Microsoft, where his primary focus has been to remove the impedance mismatch between databases and programming languages.

In the past few years I have done "legendary work" with the C# and Visual Basic teams on language and type-system support for bridging the worlds of object-oriented (CLR), relational (SQL), and hierarchical (XML) data, and of course first class functions.

L>>gmap fromFoo
L>>

module Test
  (Foo, mkFoo, fromFoo)
where
data Foo = Foo Int
mkFoo = Foo
fromFoo (Foo i) = i