"David Abrahams" wrote

"Johan Nilsson" writes:

...

Hi,

I guess that the subject line isn't even technically correct. What I'd like to do is to implement something like the following:

#define FOO(x) MyNamedParamFn(x, d = 3, e = 4)

Where e.g.

"FOO((a = 0, b = 1));"

would expand to the equivalent of:

MyNamedParamFn(a = 0, b= 1, d = 3, e = 4);

Is this possible?

Not with a C++03 preprocessor, because there's no way to "peel apart" a comma-separated list like (a = 0, b = 1) without knowing how many elements are in it. With a C99/C++0x preprocessor, you could do it.

What is possible, though, is something like: FOO_2(a = 0, b = 1) or FOO((a = 0)(b = 1)) Regards, Arkadiy

Rene Rivera wrote:

Johan Nilsson wrote:

...

Hi,

I guess that the subject line isn't even technically correct. What I'd like to do is to implement something like the following:

#define FOO(x) MyNamedParamFn(x, d = 3, e = 4)

Where e.g.

"FOO((a = 0, b = 1));"

would expand to the equivalent of:

MyNamedParamFn(a = 0, b= 1, d = 3, e = 4);

Is this possible?

What others failed to mention is that you can do this *without* macros. For example:

Actually, I need to use macros as the additional parameters actually are "line = __LINE__, file = __FILE__". Nevertheless you helped me work around the problem: #define FOO(x) MyNamedParamFn_with_named_params((x, line = __LINE__, file = __FILE__)) The above makes it work (well, at least it compiles for the time being). However I guess that this approach kind of defeats the purpose of using the BOOST_PARAMETER_(MEM)FUN macros for defining the method ... must think about that. Now if I only could get rid of those ugly double parenthesises in the call to "FOO" - guess I'll just have to wait for preprocessor variadic args support for that ... Thanks! // Johan