On 10/22/2010 12:33 PM, Warp wrote:
> Darren New<dne### [at] sanrrcom>  wrote:
>> http://journal.stuffwithstuff.com/2010/10/21/the-language-i-wish-go-was/
>
>    I'm not so sure I agree with the necessity of 'union'.
>
>    'union' in C is basically a construct which exists to save some bytes
> of memory in some rare circumstances. The price you pay for it is reduced
> type safety: You always have to make sure you are using the object with
> the correct type, or else you'll get garbage. More often than not, unions
> are not used raw, but embedded in structs, where one of the struct members
> tells the type of the union. While in some situations you can use this to
> save memory (especially if you need to instantiate this struct millions of
> times), it introduces the overhead of the type member and having to always
> check it. (Without the union there would be no need to write any conditionals
> based on the type.)
>
>    You could have the language always automatically check the proper type
> of the union, but then you'll be having overhead on every single operation
> you are doing with that union (overhead which could in many cases be avoided).
> It would be rare for the memory saving advantage to be worth the overhead.

There might be an application in which a set of classes derived from a 
common ancestor need to be forced to have the same size.  Then a member 
which is of a different type in different classes would best be a union. 
  Class member functions (late bound) would know which member of the 
union to access without having to type check.

Really, though, the union is a kludge built into C for the resource-poor 
early days of computing.

Regards,
John

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