Re: Accessing elements of static array by name

Thanks for your ideas. I know it's a common beginner mistake to care about
performance issues that can't even be measured, but looking up an
associative array at runtime, when the association can be resolved at
compile/linktime or at programm start "feels" wrong. In this case the
lookup will be orders of magnitude faster than the operation on the
element, so it wouldn't matter.

Anyway, I think I will use your idea, but instead of string-ids I will be
using an enum and be populating an id-to-object lookup-table at program
start. Similar to this:

#include <iostream>
#include <algorithm>
#include <iterator>

class A { public: int id; const char *s; };

class Array { public:
        enum Id { element_a = 0, element_b, element_c,
                element_last // Must be last
        };
private:
        static A items[];
        A *last;
        A *id2A[element_last];
public:
        Array();
        A &operator[](Id id) { return *id2A[id]; }
        A *begin() { return items; }
        A *end() { return last; }
};

A Array::items[] = {
        { element_a, "a" },
        { element_c, "c" }, // Order needn't be the same
        { element_b, "b" }, // as in enum
        { element_last, NULL } // Must be last
};

Array::Array(){
        A *it;
        for(it = items; it->id != element_last; ++it) id2A[it->id] = it;
        last = it;
}

std::ostream &operator<< (std::ostream &out, const A &a){
        return out << a.s;
}

static Array array;

int main(){
        // Access all elements
        std::copy(array.begin(),
                  array.end(),
                  std::ostream_iterator<A>(std::cout, "\n"));
        // Access elements by id
        std::cout << array[Array::element_a] << '\n'
                  << array[Array::element_b] << '\n'
                  << array[Array::element_c] << std::endl;
        return 0;
}