wayne@ames.arpa (11/02/87)
Having gotten tremendous response to my last question about #define, I
now have another one. I have a large number of manifest constants of
the form
GREATBIGLONGPREFIX_SHORTTHING
I would like to have a macro accept only SHORTTHING as an argument but
use the full constant name in the generated code. I (naively) tried
#define WIDGET(x) printf("%d\n", GREATBIGLONGPREFIX_x)
but of course this didn't work (didn't substitute x). I guess this is
related to a discussion I saw a while back on getting xy out of two
separate parameters x and y (that is, concatenation), but I don't
remember the results of that discussion well enough to apply it here.
Any assistance would as always be muchly appreciated ... Thnx.
Wayne Hathaway ultra!wayne@Ames.ARPA
Ultra Network Technologies
2140 Bering drive with a domain server:
San Jose, CA 95131 wayne@Ultra.COM
408-922-0100john@leo.UUCP ( John McCurry) (11/04/87)
In article <10104@brl-adm.ARPA>, ultra!wayne@ames.arpa (Wayne Hathaway) writes: > I have a large number of manifest constants of the form > GREATBIGLONGPREFIX_SHORTTHING > > I would like to have a macro accept only SHORTTHING as an argument but > use the full constant name in the generated code. I (naively) tried > #define WIDGET(x) printf("%d\n", GREATBIGLONGPREFIX_x) Our compiler uses the "Reiser" (spelling?) version of cpp. This version uses /**/ for concatinating things - as in: #define WIDGET(x) printf("%d\n", GREATBIGLONGPREFIX_/**/x); or #define WIDGET(x) printf("%d\n", x/**/_GREATBIGLONGSUFFIX); I don't have access to an ANSI standard compiler but our local expert says that PREFIX_##x will (should) work. I am not, by the way, a compiler guru - I just use the beasts. Any mistakes in the above posting are probably accidental. -- <insert random witticism here> John J. McCurry Computer Consoles Inc. CPD, Irvine, Ca. uunet!ccicpg!leo!john
rbutterworth@orchid.UUCP (11/05/87)
In article <10104@brl-adm.ARPA>, ultra!wayne@ames.arpa (Wayne Hathaway) writes: > I have a large number of manifest constants of > the form > GREATBIGLONGPREFIX_SHORTTHING > I would like to have a macro accept only SHORTTHING as an argument but > use the full constant name in the generated code. I (naively) tried > #define WIDGET(x) printf("%d\n", GREATBIGLONGPREFIX_x) > but of course this didn't work (didn't substitute x). Put the following into your common header file: #if defined(__STDC__) # define JOIN(x)x## #else # define JOIN(x)x #endif Then, you can do things like #define WIDGET(x) printf("%d\n", JOIN(GREATBIGLONGPREFIX_)x) This works on all the cpp implementations I've used. If you find one that it doesn't work for, you only need to add another condition for the definition of JOIN in the header file to make it work the way that that cpp wants it, and you don't have to change any of your source code.