[boost] Re: [preprocessor] BOOST_PP_IS_UNARY for Borland

From: Daniel James (daniel_at_[hidden])
Date: 2004-08-16 17:03:42

Paul Mensonides wrote:
> Note, BTW, that Borland's non-integrated command line preprocessor (i.e. not the
> compiler itself in preprocess-only mode) is a pretty good preprocessor.  It
> doesn't have the weird identifier-splicing bug that makes the straightforward
> version of IS_UNARY (etc.) not work.  Last time I checked, it can even handle
> Chaos.

That caught me out once, I thought I had some macros working on Borland, 
but it was only working on the separate preprocessor.

> Regarding the instability:  the macro itself is stable, but the input is not
> which can foul up the internals.  The library itself does a ton of extra
> scaffolding to force expansion order when it is important (for VC and MWCW < 9)
> it does this globally across the entire library.  However, that scaffolding does
> not exist in user code (nor should it have to if at all possible), and IS_UNARY
> (etc.) cannot force an arbitrary amount of expansion to account for it.  You'd
> be surprise how much stuff doesn't expand when it should on those preprocessors
> that happens to get picked up later.  

Thanks for the explanation. It'll be a big help.

 > (You might have guessed that I really
 > really hate those preprocessors.)

I can understand, I've seen the workarounds. I'm really impressed by how 
well the boost preprocessor library hides all of this.

Daniel