Macro expansion help

[Jonathan Morton]

>Could someone please "hand" generate the source code resulting when the
>following
>macro is expanded using DEFINE_HEXTILE(16)? I understand the "token passing"
>mechanism when ## is used (ie. ##bpp expands to 16) but what about bpp
>references
>not preceded by ##. And what about the second ## in
>COLOR_FROM_PIXEL##bpp##_ADDRESS(&bg)?
>Thanks for any insight.

i think, in macros, if an expansion happens 'on it's own': eg. foo(bpp);
then it doesn't need the ## token.  This would expand to foo(16);, say.
However, if it's at the end of a word, or in the middle, say: CARD##bpp
(CARD16) or FOO##bpp##BAR (FOO16BAR) it needs to be delimited by the ##
tokens to prevent it being treated as part of a larger symbol.  for example
CARDbpp wouldn't expand at all but remain as CARDbpp.

Of course, if i'm horribly wrong, someone please correct me  <grin>.  I'm
not a macro guru myself - I just attempted to figure it out from my old C
textbook.

--------------------------------------------------------------
from:     Jonathan "Chromatix" Morton
mail:     chromi "at" cyberspace.org  (not for attachments)
uni-mail: j.d.morton "at" lancaster.ac.uk

The key to knowledge is not to rely on people to teach you it.
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