Erik Wikström wrote:
> On 2007-09-25 15:26, Victor Bazarov wrote:
>> Erik Wikstr?m wrote:
>>> On 2007-09-25 14:26, Gernot Frisch wrote:
>>>> Uhm...
>>>> Is there any way of making
>>>> float pos[3];
>>>> a union of
>>>> float x,y,z;
>>>>
>>>> somehow, so I can use:
>>>>
>>>>
>>>> mything[0] = mything.y;
>>>> instead of mything.x = mything.y
>>>
>>> No, however you can do something like this:
>>>
>>> struct thing
>>> {
>>> float arr[3];
>>> float& x;
>>> float& y;
>>> float& z;
>>>
>>> thing() : x(arr[0]), y(arr[1]), z(arr[2]) {}
>>> };
>>>
>>> Which allows you to access x through either t.x or through t.arr[0]
>>> where t is an object of type thing:
>>>
>>> int main()
>>> {
>>> thing t;
>>> t.x = 1;
>>> t.y = 2;
>>> t.arr[2] = 3;
>>>
>>> int i = 0;
>>> }
>>>
>>> If you want to be able to use t[0] instead of t.arr[0] you have to
>>> overload the [] operator as Alexander Dong Back Kim suggested.
>>
>> Actually, could still do that if you do this trick:
>>
>> struct thing {
>> float x, y, z;
>> struct thing_indexing {
>> thing& t;
>> thing_indexing(thing& t) : t(t) {}
>> float& operator[](int i) {
>> return i < 2 ? i < 1 ? t.x : t.y : t.z;
>> }
>> } arr;
>> thing() : arr(*this) {}
>> thing& operator=(thing const& t) {
>> x = t.x;
>> y = t.y;
>> z = t.z;
>> }
>> };
>>
>> int main() {
>> thing t;
>> t.x = 3.1415926;
>> t.arr[1] = t.x;
>> }
>>
>> RATS! I got pulled in and am writing code when I didn't want to....
>
> Sorry, but I just cannot understand the reason for this construct. To
> me it looks like it provides exactly the same functionality as my
> code, except that I used an array and you used a struct with an
> overloaded [] operator. Please, enlighten me.

It was a facetious suggestion, so that the OP could use 'arr' to get
to the members, not just the indexing operator (working from your
original suggestion to use 'thing.arr[0]' syntax).

V
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