Array literals MUST be immutable.

Don nospam at
Wed Feb 17 01:59:00 PST 2010

grauzone wrote:
> IMHO array literals should be static arrays, which are value types. No 
> issues with heap allocation or immutability requirements.

That still wouldn't solve the performance problems.

> Don wrote:
>> (2) Concurrency issues make (1) even more important. It ought to 
>> possible to pass an array (defined at compile time) as a message.
> This sounds very special. Any example where you'd pass an array known at 
> compile time as message?

There's one in Andrei's concurrency chapter in TDPL!

>> (3) Performance of the existing array 'literals' is absolutely 
>> appalling. I doubled the speed of my entire app by changing ONE array 
>> declaration from 'immutable [] xxx' into 'static const [] xxx'!!!
>> Right now, if an array literal appears in your code, chances are it's 
>> a performance bug. It's deceptive that there's a hidden heap 
>> allocation happening in every array literal. It's got no business 
>> being in a systems language IMHO.
> Delegates also can have hidden allocation (basically, you have to guess 
> the compiler's guess whether a delegate is a real closure). There are 
> several language elements that may or may not trigger additional memory 
> allocations (like setting .length or the ~= operator).
> And the underlying problem is the bad GC that is torturing us all, isn't 
> it?

No, this one has nothing to do with the GC. The problem is that there's 
no way of saying 'this array literal is not a variable'.

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