John Carmack applauds D's pure attribute

[Sean Kelly]

Slicing works, it just requires more care. GC makes slicing work pretty much automatically, though you can end up with severe memory bloat. 

On Mar 6, 2012, at 6:25 PM, Walter Bright <newshound2 at digitalmars.com> wrote:

> On 3/6/2012 4:27 AM, Manu wrote:
>> On 26 February 2012 00:55, Walter Bright <newshound2 at digitalmars.com
>>    Most straight up GC vs malloc/free benchmarks miss something crucial. A GC
>>    allows one to do substantially *fewer* allocations. It's a lot faster to not
>>    allocate than to allocate.
>> Do you really think that's true?
> 
> Yes.
> 
>> Are there any statistics to support that?
> 
> No, just my experience using both.
> 
> Consider strings. In C, I'd often have a function that returns a string. The caller then (eventually) free's it. That means the string must have been allocated by malloc. That means that if I want to:
> 
>   return "foo";
> 
> I have to replace it with:
> 
>   return strdup("foo");
> 
> It means I can't do the "small string" optimization. It means I cannot return the tail of some other string. I cannot return a malloc'd string that anything else points to. I *must* return a *unique* malloc'd string.
> 
> This carries into a lot of data structures, and means lots of extra allocations.
> 
> Next problem: I can't do array slicing. I have to make copies instead.
> 
> You suggested using ref counting. That's only a partial solution. Setting aside all the problems of getting it right, consider getting a stream of input from a user. With GC, you can slice it and store those slices in a symbol table - no allocations at all. No chance of that without a GC, even with ref counting.