Mixin statements

[Tofu Ninja via Digitalmars-d]

On Friday, 12 June 2015 at 14:22:45 UTC, Jacob Carlborg wrote:
> On 2015-06-12 10:06, Tofu Ninja wrote:
>> Also a feature that would make this perfect is macro template 
>> arguments.
>>
>> Something like
>>
>> void templateFunction(macro a)()
>> {
>>      int x = 5;
>>      return mixin(a);
>> }
>>
>> Essentially, the expression in the argument would be converted 
>> to an
>> expression macro.
>>
>> Calling templateFunction!(x + x)() would return 10
>>
>> Why would you want this over string mixins?
>> For one, it looks a lot cleaner.
>> Also as its not a string, it cant be changed and the parser 
>> need not
>> re-parse it when it gets mixed in, which could be faster than 
>> normal
>> string mixins.
>> Also it would allow for mixin macros to look something similar 
>> to c++
>> macros only with the mixin keyword in front of it. Would keep 
>> the whole
>> thing clean looking.
>>
>> Example assert doing c style return error codes.
>>
>> mixin macro cassert(macro expression, alias errorcode)
>> {
>>      if(!(mixin(expression))) return errorcode;
>> }
>>
>> ... some other piece of code that returns null on error ...
>> mixin cassert(x == 3, null);
>
> This starts to look like AST macros to me.

But without the AST ;) never actually have to deal with ast's but 
still has a lot of its functionality in a simpler form.