lvalue - opIndexAssign - Tango

[downs]

The Anh Tran wrote:
> Hi,
> 
> When porting from c++ to D, i encounter this strange discrimination:
> 1. Built-in AA:
>     int[int] arr;
>     arr[123] += 12345;
>     arr[321]++;
> 
> 2. Tango HashMap:
>     auto hm = new HashMap!(int, int)();
>     hm[123] += 12345; // error not lvalue
>     hm[123]++;    // error
> 
> D document says current opIndexAssign does not work as lvalue. But why
> can builtin AA can that? How can i copy builtin AA behaviour?
> 

Take a look at tools.behave_as (for phobos).

It only works properly with built-in types though.

http://dsource.org/projects/scrapple/browser/trunk/tools/tools/behave_as.d

It should let you implement a HashMap that supports += and similar, at least for built-ins.