metaprogramming question

[fawcett at uwindsor.ca]

On 10-04-19 01:31 AM, BCS wrote:
> Hello Justin Spahr-Summers,
>
>> On Mon, 19 Apr 2010 00:12:28 +0000 (UTC), Graham Fawcett
>> <fawcett at uwindsor.ca> wrote:
>>
>>> Hi folks,
>>>
>>> I'd like to wrap a family of C functions that look like this:
>>>
>>> gboolean fooXXX(arg1, ..., argN, GError** err)
>>>
>>> Their signatures and arities vary, but they all have a GError** as
>>> their last argument. If a function returns false, then 'err' will be
>>> set to a relevant Error struct.
>>>
>>> I would like to write a wrapper that would let me call these
>>> functions sort of like this:
>>>
>>> check!(fooXXX(arg1, ..., argN))
>>>
>>> where the 'check' expression would be equivalent to:
>>>
>>> GError* err;
>>> bool ok = fooXXX(arg1, ..., argN, &err);
>>> if (!ok)
>>> throw new Exception((*err).message);
>>> Does D (2.0) offer a metaprogramming technique I could use to
>>> accomplish this -- particularly, to inject that 'err' argument into
>>> the tail of the fooXXX call?
>>>
>>> Thanks,
>>> Graham
>> You can use some expression tuple magic to accomplish something like
>> that:
>>
>> bool check(alias func, EL ...)() {
>> GError* err;
>> bool ok = func(EL, &err);
>> if (!ok)
>> throw new Exception((*err).message);
>> return ok;
>> }
>> // used like:
>> check!(fooXXX, arg1, ..., argN);
>
> IIRC that should be:
>
> check!(fooXXX, argType1, ..., argTypeN)(arg1, ..., argN);
>
>> See http://digitalmars.com/d/2.0/template.html#TemplateTupleParameter
>>
>
> Or you can mangel that a bit:
>
> template check(alias func) {
> bool check(EL ...)() {
> GError* err;
> bool ok = func(EL, &err);
> if (!ok)
> throw new Exception((*err).message);
> return ok;
> }
> }
>
> that should allow you to call it like:
>
> check!(fooXXX)(arg1, ..., argN);
>

Remarkable! Thank you to everyone who responded. I can't wait to give
these a try tonight. :)

Cheers,
Graham