functional way doing array stuff/ lambda functions

[Namal via Digitalmars-d-learn]

Hello guys,

I am still uncertain how to do it right when it comes to lambda 
functions. For instance: how do I multiply all the elements in an 
array ?

int product(const ref int[] arr){

        int p = 1;
        foreach(i;arr)
                p*=i;
        return p;
}