Comment by ajtulloch | Hacker News Reader

Comment by ajtulloch | Hacker News Reader

Using Facebook's `folly::gen` library [1], you can get it down to:

    vector<int> squareVec3(const vector<int>& v) {
      return from(v) | mapped([](int i){ return i * i; }) | as<vector>();
    }

which is pretty slick. There are a bunch of the usual LINQ/functional operators in `folly::gen` that are quite nice. As an example, to filter out the odd elements of `v`, you can do

    vector<int> squareVecFiltered(const vector<int>& v) {
      return from(v) 
           | filter([](int i){ return i % 2 == 0; })
           | mapped([](int i){ return i * i; })  
           | as<vector>();
    }

https://github.com/facebook/folly/tree/master/folly/gen

Or using [Linq](https://github.com/pfultz2/Linq):

    vector<int> squareVec(const vector<int>& v)
    {
        return LINQ(from(i, v) select(i*i)) | linq::to_container;
    }

And also filtering out odd elements:

    vector<int> squareVecFiltered(const vector<int>& v)
    {
        return LINQ(from(i, v) where(i % 2 == 0) select(i*i)) | linq::to_container;
    }

That's cool, but I'd rather not bitwise-or my functional operators together. Something like this would be better:

    vector<int> squareVecFiltered(const vector<int>& v) {
      return from(v
           filter([](int i){ return i % 2 == 0; }),
           mapped([](int i){ return i * i; }),
           as<vector>());
    }

That is actually really nice.

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