Non-Initialized Dynamic Arrays Construction

[TheFlyingFiddle]

On Monday, 24 February 2014 at 13:08:52 UTC, Mengu wrote:
> On Monday, 24 February 2014 at 11:29:39 UTC, bearophile wrote:
>> TheFlyingFiddle:
>>
>>> http://dlang.org/phobos/std_array.html#.uninitializedArray is 
>>> what you want.
>>
>> The OP wants minimallyInitializedArray. uninitializedArray is 
>> only for special situations. Perhaps we have to fix the online 
>> docs to underline this.
>>
>> Bye,
>> bearophile
>
> what's the difference?

Well for anything that does not have indirections eg numbers / 
chars and structs without classes/arrays/pointers in them. Then 
the two functions are equivalent.

So:

int[] first  = uninitializedArray!(int[])(n);
int[] second = minimallyInitializedArray!(int[])(n);

Both first and second contain garbaged values.

int*[] third = uninitializedArray!(int*[])(n);
int*[] forth = minimallyInitializedArray!(int*[])(n);

The third array contains garbage but all elements in forth are 
initialized to null.

I assume this behavior is this way since an int with a garbage 
value is not as bad as a garbage pointer dereference into memory.

>> The OP wants minimallyInitializedArray. uninitializedArray is 
>> only for special situations.

True but uninitializedArray corresponds to = void semantics for 
all arrays.
minimallyInitializedArray is safer though so i guess it should be 
used.

>>Wouldn't it be nice to have some kind of syntactic sugar for 
>>this similar to what we have for static arrays?
>>
>>BTW: Why isn't simply the following allowed?
>>
>>  int n = 3;
>>  int[n] = void;
>>
>>Is it too easy to confuse with static array syntax?

I don't like this, since it would be wierd from an allocation 
view point. How is int[n] allocated? Is it the GC? Is it alloca? 
Can i overide the allocation mechanism? Does the allocated array 
behave the same as a static array? (it gets destroyed if it goes 
out of scope)

I think it gets a little confusing and also personally i don't 
want more hidden memory allocations. We already have alot of 
those.