nigel@cnw01.storesys.coles.oz.au (Nigel Harwood) (06/19/91)
Does anyone know if you can append strings in ANSI C.
For example I want a macro which appends one of its numeric
arguments to a string coded into the marco.
#define APPEND(x,v) { donothing+x = v; }
I know that the '+' isn't what I'm after but using whatever the method
turns out to be what I want it to generate from APPEND(1,123) is:
{ donothing1 = 123; }
Anyone know the secret ?
Regards
--
<<<<<<<<<<<<<<<<<<<<<<<<< Nigel Harwood >>>>>>>>>>>>>>>>>>>>>>>>>>>
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<< FAX: +61 3 829 6886 >>pckim@unisql.UUCP (Pyung-Chul Kim) (06/20/91)
In article <1271@cnw01.storesys.coles.oz.au> nigel@cnw01.storesys.coles.oz.au (Nigel Harwood) writes: >Does anyone know if you can append strings in ANSI C. > >For example I want a macro which appends one of its numeric >arguments to a string coded into the marco. > >#define APPEND(x,v) { donothing+x = v; } > >I know that the '+' isn't what I'm after but using whatever the method >turns out to be what I want it to generate from APPEND(1,123) is: > > { donothing1 = 123; } > FAQ 37. says that we can use ## for this purpose. 37. I have some old code that tries to construct identifiers with a macro like "#define Paste(a, b) a/**/b", but it doesn't work any more. A: Try the ANSI token-pasting operator ##. That is, #define APPEND(x,v) { donothing ## x = v; } Hope it helps -- Pyung-Chul Kim UniSQL, Inc. 9390 Research Blvd., Kaleido II, Suite 220, Austin, TX 78759 Internet: execu!sequoia!unisql!pckim@cs.utexas.edu UUCP: {uunet, cs.utexas.edu!execu}!sequoia!unisql!pckim TEL: (512)343-7297 Ext. 332 FAX: (512)343-7383
hp@vmars.tuwien.ac.at (Peter Holzer) (06/20/91)
nigel@cnw01.storesys.coles.oz.au (Nigel Harwood) writes: >Does anyone know if you can append strings in ANSI C. >For example I want a macro which appends one of its numeric >arguments to a string coded into the marco. >#define APPEND(x,v) { donothing+x = v; } Nitpick: I do not see any strings here, just tokens (a string is something between double quotes) >I know that the '+' isn't what I'm after but using whatever the method >turns out to be what I want it to generate from APPEND(1,123) is: > { donothing1 = 123; } >Anyone know the secret ? Yes. The token pasting operator is ##. So your macro should read: #define APPEND(x,v) {donothing ## x = v;} -- | _ | Peter J. Holzer | Think of it | | |_|_) | Technical University Vienna | as evolution | | | | | Dept. for Real-Time Systems | in action! | | __/ | hp@vmars.tuwien.ac.at | Tony Rand |
fischer@iesd.auc.dk (Lars P. Fischer) (06/21/91)
>>>>> On 19 Jun 91, nigel@cnw01.storesys.coles.oz.au (Nigel Harwood) said:
Nigel> Does anyone know if you can append strings in ANSI C.
"The preprocessor operator ## provides a way to concatenate actual
arguments during macro expansion. [...]
#define paste(front, back) front ## back"
- Kernighan & Ritchie: The C Programming Language, 2.ed, p.90
Found by looking up "concatenate" in the index.
RTFM.
/Lars
--
Lars Fischer, fischer@iesd.auc.dk | It takes an uncommon mind to think of
CS Dept., Univ. of Aalborg, DENMARK. | these things. -- Calvinbruno@sdcc10.ucsd.edu (Bruce W. Mohler) (06/21/91)
In article <FISCHER.91Jun20221733@galilei.iesd.auc.dk> fischer@iesd.auc.dk (Lars P. Fischer) writes: >>>>>> On 19 Jun 91, nigel@cnw01.storesys.coles.oz.au (Nigel Harwood) said: > >Nigel> Does anyone know if you can append strings in ANSI C. > >"The preprocessor operator ## provides a way to concatenate actual > arguments during macro expansion. [...] > > #define paste(front, back) front ## back" > > - Kernighan & Ritchie: The C Programming Language, 2.ed, p.90 > >Found by looking up "concatenate" in the index. > >RTFM. > >/Lars >-- >Lars Fischer, fischer@iesd.auc.dk | It takes an uncommon mind to think of >CS Dept., Univ. of Aalborg, DENMARK. | these things. -- Calvin What options do I have if my preprocessor does not support "##"? I've tried having the 2 strings sandwiched between empty comments ("/**/"). Any suggestions? Bruce -- Bruce W. Mohler Systems Programmer (aka Staff Analyst) bruno@sdcc10.ucsd.edu voice: 619-586-2218
Dave.Harris@f14.n15.z1.fidonet.org (Dave Harris) (06/22/91)
>From: nigel@cnw01.storesys.coles.oz.au (Nigel Harwood) >Does anyone know if you can append strings in ANSI C. >For example I want a macro which appends one of its numeric >arguments to a string coded into the marco. >#define APPEND(x,v) { donothing+x = v; } >I know that the '+' isn't what I'm after but using whatever the method >turns out to be what I want it to generate from APPEND(1,123) is: > { donothing1 = 123; } >Anyone know the secret ? The secret is to use an array (like donothing[5]) or a lookup table. This would be considered a better style unless you are using this differently than I think you are trying to use this.... but... Mine is not the place to ask. #define APPEND(x,v) donothing##x = v -- Uucp: ...{gatech,ames,rutgers}!ncar!asuvax!stjhmc!15!14!Dave.Harris Internet: Dave.Harris@f14.n15.z1.fidonet.org
sarima@tdatirv.UUCP (Stanley Friesen) (06/25/91)
In article <20832@sdcc6.ucsd.edu> bruno@sdcc10.ucsd.edu (Bruce W. Mohler) writes: >What options do I have if my preprocessor does not support "##"? >I've tried having the 2 strings sandwiched between empty comments >("/**/"). > >Any suggestions? What preprocessor do you have? Seriously, every non-ANSI preprocessor known does this differently ( at least for all practical purposes). Once we know the vendor, version and OS in question, we *might* be able to give you an answer. -- --------------- uunet!tdatirv!sarima (Stanley Friesen)