Will there be any official LINQ like lambda based library for C++?

Question

Given C++('11) has lambdas now, will there be any LINQ like higher order function library officially supported later? Is there any such library now being used in any production level code?

Obviously I'm not expecting the SQL-like expression tree based LINQ query syntax in C++. I am talking about the lambda based one. So, no new language feature in needed in C++'11, just a library will do.

Answer 1

LINQ-to-objects is already supported in the Standard library and has been since it's inception. The syntax is just a bit different- it was never intended to emulate SQL and has way too many iterators in it. You can make it more reminiscent without too big a hassle.

Edit: When actually attempting to make it more reminiscent without too big a hassle, I determined that it actually could be a significant hassle. It is, however, still completely possible.

Answer 2

Notes : For C++2011 there is not such functionality. Fortunately, the next C++ should include a filesystem library (see boost::filesystem) so you can guess that such a database library will not be standardized soon.

There are several (and some recent) discussions on the boost mailing list about such library. Several people are pointing to potential boost-like libraries like SOCI and CPPDB.

Also, I don't see how lambdas can help for such a functionality. Lambdas are still code, not EDSL constructs.

Answer 3

There's ODB which is interesting.

see the sample code from the ODB wikipedia entry that searches for all people called Doe younger than 30 (age and last are DB columns, directly mapped to a class, this is done by the ODB compiler to it always keeps automatically generated classes in sync with the DB schema, without having to modify a DB->code mapping definition file or assembly). I like it because of that, having had to maintain an Entity Framework assembly.

  transaction t(db.begin ());

  result r(db.query<person>(query::last == "Doe" && query::age < 30));

  for (result::iterator i (r.begin ()); i != r.end (); ++i)
  {
    cout << "Hello, " << i->first () << endl;
  }

  t.commit ();