Higher-order functions?

[Nick Sabalausky]

"Jonas H." <jonas at lophus.org> wrote in message 
news:mailman.1600.1334099651.4860.digitalmars-d-learn at puremagic.com...
> Hi everyone,
>
> does D have any runtime higher-order function facilities? (I'm not talking 
> about templates.)
>

Yes. Fully. Many are already in the std lib: 
http://dlang.org/phobos/std_algorithm.html

> More specifically, is something like this possible? (That's how I'd do it 
> in Python)
>
> car_prices = map(Car.get_price, list_of_cars)
>

Just as one example (These all work as of DMD 2.058):

    import std.algorithm; // For 'map'

    class Car {...blah...}
    int getPrice(Car c) {return ...blah...;}

    void main()
    {
        auto listOfCars = [new Car()];
        auto carPrices = listOfCars.map!getPrice();
    }

Or:

    import std.algorithm; // For 'map'

    class Car
    {
        ...blah...
        @property int price() {return ...blah...;}
    }

    void main()
    {
        auto listOfCars = [new Car()];

        auto carPrices = listOfCars.map!( (Car c) => (c.price) )();
        //or
        auto getPrice = (Car c) => (c.price); // getPrice can be reassigned 
at runtime
        auto carPrices = listOfCars.map!getPrice();
    }

> car = new Car
> foobar(car.get_price)

    class Car
    {
        ...blah...
        int getPrice() {return ...blah...;}
    }
    void foobar(int delegate() dg)
    {
        auto x = dg();
    }
    void main()
    {
        auto car = new Car();
        foobar(&car.getPrice);
    }