Possible way to achieve lazy loading with const objects

[Simen Kjaeraas]

On Mon, 26 Sep 2011 02:02:06 +0200, Simen Kjaeraas  
<simen.kjaras at gmail.com> wrote:

> On Sat, 24 Sep 2011 13:19:33 +0200, Peter Alexander  
> <peter.alexander.au at gmail.com> wrote:
>
>> Lazy loading and caching are the same thing.
>>
>> struct Foo
>> {
>>      T m_lazyObj = null;
>>      bool m_isLoaded = false;
>>
>>      T getObj()
>>      {
>>          if (!m_isLoaded)
>>          {
>>              m_lazyObj = func();
>>              m_isLoaded = true;
>>          }
>>          return m_lazyObj;
>>      }
>> }
>>
>> Change m_lazyObj to m_cachedObj and m_isLoaded to m_isCached and you  
>> have caching.
>
> This is too simple. If the system also rewrites all members to  
> @properties that
> sets m_isLoaded = true, it might work. Example:
>
> struct S {
>      int n;
>      lazy int otherN = () { return n + 2; } // compile time error here  
> if you refer to lazily initialized members.
> }
>
> =>
>
> struct S {
>      int __n;
>      int __otherN;
>      bool __otherNloaded = false;
>
>
>      @property
>      int n( ) {
>          return __n;
>      }
>
>      @property
>      int n(int value) {
>          if (__n != value) {
>              __n = value;
>              __otherNloaded = false;
>          }
>          return __n;
>      }
>
>      @property
>      int otherN( ) {
>         if (!__otherNloaded) {
>             __otherN = () { return n + 2; }();
>             __otherNloaded = true;
>         }
>         return __otherN;
>      }
> }
>
> Now, the overhead might be troublesome, but this seems to me to work.

Oh, and of course more stuff is need if you try to make this work across  
threads.


-- 
   Simen