BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Is it possible to pass an anonymous ary to a function?          BorlandTalk.com Forum Index -> C++ Builder (Language C++) View previous topic :: View next topic   Author Message Guest Posted: Tue Dec 19, 2006 9:10 am    Post subject: Is it possible to pass an anonymous ary to a function? I am wondering, if it is possible to pass an anonymous ary to a function? Having a function declaration void fct(int[]); the following forks fine: int a[]={1,2,3}; fct(a); Can I pass {1,2,3} somehow without temporarily storing it inside a var? E.g. I tried fct(int[]({1,2,3})); but this doesn't work ~~~~~~~~~~ As a following step I would like to pass the number of the array-indices void fct(int ary[], size_t ary_size); The working non-anonymouse-var-version would be #define TUPEL_ARY_SIZE(ary) ary, sizeof(ary)/sizeof(*ary) int a[]={1,2,3}; fct(TUPEL_ARY_SIZE(a)); ~~~~~~~~~~ It's just a tryout: if the result looks too ugly, I would use the working version above... Thanks, Michael Back to top Remy Lebeau (TeamB) Guest Posted: Tue Dec 19, 2006 9:10 am    Post subject: Re: Is it possible to pass an anonymous ary to a function? <MR> wrote in message news:rc0fo29igfb822hs8daarostu35fq09t5r (AT) 4ax (DOT) com... Quote: I am wondering, if it is possible to pass an anonymous ary to a function? Not that I know of, no. Gambit Back to top Thomas Maeder [TeamB] Guest Posted: Tue Dec 19, 2006 11:14 pm    Post subject: Re: Is it possible to pass an anonymous ary to a function? <MR> writes: Quote: I am wondering, if it is possible to pass an anonymous ary to a function? Having a function declaration void fct(int[]); the following forks fine: int a[]={1,2,3}; fct(a); Can I pass {1,2,3} somehow without temporarily storing it inside a var? No. Can you give an example that shows why this would be useful? Quote: ~~~~~~~~~~ As a following step I would like to pass the number of the array-indices void fct(int ary[], size_t ary_size); The working non-anonymouse-var-version would be #define TUPEL_ARY_SIZE(ary) ary, sizeof(ary)/sizeof(*ary) int a[]={1,2,3}; fct(TUPEL_ARY_SIZE(a)); Have you looked at std::vector and/or Boost.Array (cf. http://www.boost.org/)? Quote: It's just a tryout: if the result looks too ugly, I would use the working version above... I would advise against it. Consider void g(int ints[], std::size_t nrOfInts) { } void f(int ints[]) { g(TUPEL_ARY_SIZE(ints)); // passes wrong value for nrOfInts } int main() { int ints[] = {1,2,3}; f(ints); } If anything, I nowadays prefer to use something like #include <cstddef> template <typename T, std::size_t N> char (&array_sizer(T const (&)[N]))[N]; void g(int ints[], std::size_t nrOfInts) { } void f(int ints[]) { g(ints, sizeof array_sizer(ints)); // compiler error; ints is not an array } int main() { int ints[] = {1,2,3}; f(ints); g(ints, sizeof array_sizer(ints)); // ok } array_sizer is a function taking as argument a reference to an array of N Ts; it's return type is a reference to an array of N chars; sizeof such a char array is N, and since sizeof is evaluated at compile time, array_sizer isn't called and needn't be defined. Back to top Alex Bakaev [TeamB] Guest Posted: Wed Dec 20, 2006 1:06 am    Post subject: Re: Is it possible to pass an anonymous ary to a function? Thomas Maeder [TeamB] wrote: Quote: template <typename T, std::size_t N char (&array_sizer(T const (&)[N]))[N]; Both bcc and comeau complain that this function doesn't return a value. VC++ doesn't. I don't know what gcc says. ..a p.s. I've used this for quite some time and find it very useful Back to top Chris Uzdavinis (TeamB) Guest Posted: Wed Dec 20, 2006 1:40 am    Post subject: Re: Is it possible to pass an anonymous ary to a function? "Alex Bakaev [TeamB]" <zxtt (AT) att (DOT) net> writes: Quote: Thomas Maeder [TeamB] wrote: template <typename T, std::size_t N char (&array_sizer(T const (&)[N]))[N]; Both bcc and comeau complain that this function doesn't return a value. VC++ doesn't. I don't know what gcc says. .a Strange, Comeau compiles it cleanly for me. What version are you using? Is it possible that the warning comes from the underlying C compiler? -- Chris (TeamB); Back to top Duane Hebert Guest Posted: Wed Dec 20, 2006 2:05 am    Post subject: Re: Is it possible to pass an anonymous ary to a function? "Alex Bakaev [TeamB]" <zxtt (AT) att (DOT) net> wrote in message news:458837ea (AT) newsgroups (DOT) borland.com... Quote: Thomas Maeder [TeamB] wrote: template <typename T, std::size_t N char (&array_sizer(T const (&)[N]))[N]; Both bcc and comeau complain that this function doesn't return a value. VC++ doesn't. I don't know what gcc says. Comeau online test compiles it cleanly for me after adding the include: #include <cstddef> template <typename T, std::size_t N> char (&array_sizer(T const (&)[N]))[N]; int main() {} Your Comeau C/C++ test results are as follows: Comeau C/C++ 4.3.8 (Aug 19 2006 13:36:4 for ONLINE_EVALUATION_Alpha1 Copyright 1988-2006 Comeau Computing. All rights reserved. MODE:strict errors C++ In strict mode, with -tused, Compile succeeded (but remember, the Comeau online compiler does not link). Back to top Alex Bakaev [TeamB] Guest Posted: Wed Dec 20, 2006 7:01 am    Post subject: Re: Is it possible to pass an anonymous ary to a function? Duane Hebert wrote: Quote: Comeau online test compiles it cleanly for me after adding the Here it is: "ComeauTest.c", line 3: warning: missing return statement at end of non-void function "char_array_size(const T (&)[N]) [with T=T, N=N]" char const (& char_array_size( T const (&)[N] ) ) [N] { } code: template <typename T, const size_t N> char const (& char_array_size( T const (&)[N] ) ) [N] { } I see the difference. In my case it's actual function with the body. Case solved :) ..a Back to top Duane Hebert Guest Posted: Wed Dec 20, 2006 7:18 am    Post subject: Re: Is it possible to pass an anonymous ary to a function? "Alex Bakaev [TeamB]" <zxtt (AT) att (DOT) net> wrote in message news:45888b2d$1 (AT) newsgroups (DOT) borland.com... Quote: Duane Hebert wrote: Comeau online test compiles it cleanly for me after adding the Here it is: "ComeauTest.c", line 3: warning: missing return statement at end of non-void function "char_array_size(const T (&)[N]) [with T=T, N=N]" char const (& char_array_size( T const (&)[N] ) ) [N] { } code: template <typename T, const size_t N char const (& char_array_size( T const (&)[N] ) ) [N] { } I see the difference. In my case it's actual function with the body. 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