Is there a LINQ library for C++? [closed]

Answer 1

Linq++ by Hong Jiang looks like a good start. Its syntax is much closer to Linq than CLinq's. Linq by pfultz2 looks interesting, as well, but it needs a C++11 compiler.

Answer 2

C++ 0x, or whatever it ends up being called, does have a new keyword called auto which allows for type-inference. And yes, there will be lambda's coming for C++. Also, a quick Google search revealed this, CLinq.

Answer 3

I have written a small library cppLinq that reimplements IEnumerable<> and its LINQ operators. It is just an experiment; for now it only works on Windows (coroutines are implemented with Win32 fibers), and only builds with the Dev Preview of VS11 (it makes an heavy usage of lambda expressions :-)).

It allows to write code like this:

auto source = IEnumerable<int>::Range(0, 10);

auto it = source->Where([](int val) { return ((val % 2) == 0); })
                ->Select<double>([](int val) -> double { return (val * val); }));

foreach<double>(it, [](double& val){
    printf("%.2f\n", val);
});

Answer 4

Microsoft has just announced that they've built LINQ for C and C++. Not yet available, though.

Update 11/06/2012:

Microsoft Open Technologies, Inc. has now released and open-sourced (Apache License 2.0) a number of related libraries, including a LINQ implementation (Ix++), and it's new Reactive Extensions (Rx++) library.

Answer 5

http://cpplinq.codeplex.com/ is a very good implementation.
From the author:
The motivation for CppLinq is that both boolinq and Native-RX seems to be based around the operator"." to compose list functions. The problem is that the "." operator is that it can't be overloaded in C++ which makes it hard to extend these libraries with functions of my own design. To me this is important. CppLinq is based around operator>> which is overloadable thus CppLinq can be made extensible.

Answer 6

Actually if you just want to use Linq for list comprehension, you can use this Linq library. It requires C++11(it will work in MSVC 2010 though) and Boost. With the library you can write linq queries like this:

struct student_t
{
    std::string last_name;
    std::vector<int> scores;
};

std::vector<student_t> students = 
{
    {"Omelchenko", {97, 72, 81, 60}},
    {"O'Donnell", {75, 84, 91, 39}},
    {"Mortensen", {88, 94, 65, 85}},
    {"Garcia", {97, 89, 85, 82}},
    {"Beebe", {35, 72, 91, 70}} 
};

auto scores = LINQ(from(student, students) 
                   from(score, student.scores) 
                   where(score > 90) 
                   select(std::make_pair(student.last_name, score)));

for (auto x : scores)
{
    printf("%s score: %i\n", x.first.c_str(), x.second);
}

Which will output:

Omelchenko score: 97
O'Donnell score: 91
Mortensen score: 94
Garcia score: 97
Beebe score: 91