To help LDC/GDC

[deadalnix]

On Monday, 8 April 2013 at 15:07:31 UTC, Jacob Carlborg wrote:
> On 2013-04-08 14:52, Iain Buclaw wrote:
>> On 8 April 2013 13:25, Jacob Carlborg <doob at me.com 
>> <mailto:doob at me.com>>
>> wrote:
>>
>>    On 2013-04-08 10:29, Iain Buclaw wrote:
>>
>>        This information could possibly be helpful.  Though 
>> given that
>>        most of
>>        (gdc) codegen is on par with g++, there's probably not 
>> much on
>>        the list
>>        that isn't already detected by the backend optimisation 
>> passes.
>>
>>
>>    Multiple calls to pure functions could be cached.
>>
>>    --
>>    /Jacob Carlborg
>>
>>
>> Not always, but in some circumstances, yes.
>>
>> ---
>> struct Foo
>> {
>>   int a = 0;
>>   pure int bar (immutable int x)
>>   {
>>     ++a;
>>     return x * 2;
>>   }
>> }
>>
>>
>> void main()
>> {
>>   Foo f;
>>   int i = f.bar(2) + f.bar(2);
>>
>>   assert (i == 8);
>>   assert (f.a == 2);
>> }
>
> I though that wasn't possible. What's the point of pure if 
> that's possible?

You have to think that this is an hidden parameter. The function 
touch that parameter, no global state.