Array literals' default type

[Yigal Chripun]

On 10/10/2009 10:11, Don wrote:
> Christopher Wright wrote:
>> Don wrote:
>>> I don't understand why runtime-determined array literals even exist.
>>> They're not literals!!!
>>> They cause no end of trouble. IMHO we'd be *much* better off without
>>> them.
>>
>> You don't see the use. I do. I would go on a murderous rampage if that
>> feature were removed from the language.
>>
>> For example, one thing I recently wrote involved creating a process
>> with a large number of arguments. The invocation looked like:
>> exec("description", [procName, arg1, arg2] ~ generatedArgs ~ [arg3,
>> arg4] ~ moreGeneratedArgs);
>>
>> There were about ten or fifteen lines like that.
>>
>> You'd suggest I rewrite that how?
>> char[][] args;
>> args ~= procName;
>> args ~= arg1;
>> args ~= arg2;
>> args ~= generatedArgs;
>> args ~= arg3;
>
> Of course not. These runtime 'array literals' are just syntax sugar for
> a constructor call. Really, they are nothing more.
> At worst, it would be something like:
>
> exec("description", createArray(procName, arg1, arg2) ~ generatedArgs ~
> createArray(arg3, arg4) ~ moreGeneratedArgs);
>
> Depending on what the 'exec' signature is, it could be simpler than
> that. But that's the absolute worst case.
>
> The language pays a heavy price for that little bit of syntax sugar.
>

You keep calling these literals "constructor calls' and I agree that 
that's what they are. My question is then why not make them real 
constructors?

auto a = new int[](x, y, z);
auto b = new int[3](x, y, z);
auto c = new int[]; // empty array
auto d = new int[3]; // use default ctor: d == [0,0,0]

for arrays of class instances this could be extended to call a 
constructor for each index, something like:

// tuples would be very handy here..
auto e = new Class[2](Tuple!(args1), Tuple!(args2));