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Re: concatenate variable number of arguments and types to a char *

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On 19.08.2011 06:50, Felix Bytow wrote:
> Am 19.08.2011 06:04, schrieb suresh:
>> Hi
>> How to write a function which would concatenate variable number of arguments of different type and return a char *. For example I need the function
>>
>> f("his weight is = ", 51.5, "pounds");
>>
>> to return the string "his weight is =  51.5 pounds".
>>
>> thanks
>> suresh
>
> Hi,
> this might do, what you want:
>
> #include<string>
> #include<sstream>
> #include<iostream>
>
> template<typename Head>
> std::string concat(Head const&  head)
> {
> 	std::stringstream strm;
> 	strm<<  head;
> 	return strm.str();
> }
>
> template<typename Head, typename... Tail>
> std::string concat(Head const&  head, Tail... tail)
> {
> 	return (concat(head) + concat(tail...));
> }
>
> int main(void)
> {
> 	std::cout<<  concat("The answer is ", 42, "!")<<  std::endl;
> 	return 0;
> }
>
> Ofcourse this code makes use of variadic templates which are part of
> C++11. You will find that not all compilers support that already.
>
> Using the old tools you will not be able to write a function that fits
> your needs completely...

The C++98 solution I posted is more efficient, O(n) versus yours O(n^2), 
at the cost of slightly different notation.

The C++0x machinery you're using can be used to wrap such a more 
efficient solution in order to get conventional usage notation.

However I think the C++98 solution is OK as it is... ;-)


Cheers & hth.,

- Alf

PS: Please replace tab characters with spaces before posting. Many 
editors do that with just a few keypresses.

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concatenate variable number of arguments and types to a char * suresh <suresh.amritapuri@gmail.com> - 2011-08-18 21:04 -0700
  Re: concatenate variable number of arguments and types to a char * "Alf P. Steinbach" <alf.p.steinbach:usenet@gmail.com> - 2011-08-19 06:26 +0200
  Re: concatenate variable number of arguments and types to a char * Felix Bytow <felix.bytow@informatik.tu-chemnitz.de> - 2011-08-19 06:50 +0200
    Re: concatenate variable number of arguments and types to a char * "Alf P. Steinbach" <alf.p.steinbach:usenet@gmail.com> - 2011-08-19 08:04 +0200
  Re: concatenate variable number of arguments and types to a char * PaulR <pchristor@yahoo.co.uk> - 2011-08-19 04:01 -0700
    Re: concatenate variable number of arguments and types to a char * Leigh Johnston <leigh@i42.co.uk> - 2011-08-19 14:00 +0100
      Re: concatenate variable number of arguments and types to a char * Juha Nieminen <nospam@thanks.invalid> - 2011-08-19 14:31 +0000
        Re: concatenate variable number of arguments and types to a char * "Alf P. Steinbach" <alf.p.steinbach:usenet@gmail.com> - 2011-08-19 16:57 +0200
          Re: concatenate variable number of arguments and types to a char * Juha Nieminen <nospam@thanks.invalid> - 2011-08-19 19:15 +0000
        Re: concatenate variable number of arguments and types to a char * Leigh Johnston <leigh@i42.co.uk> - 2011-08-19 16:33 +0100
          Re: concatenate variable number of arguments and types to a char * Juha Nieminen <nospam@thanks.invalid> - 2011-08-19 19:18 +0000
            Re: concatenate variable number of arguments and types to a char * Leigh Johnston <leigh@i42.co.uk> - 2011-08-19 20:29 +0100
              Re: concatenate variable number of arguments and types to a char * Paul <pchristor@yahoo.co.uk> - 2011-08-19 14:18 -0700
                Re: concatenate variable number of arguments and types to a char * Leigh Johnston <leigh@i42.co.uk> - 2011-08-19 22:37 +0100
                Re: concatenate variable number of arguments and types to a char   * Ian Collins <ian-news@hotmail.com> - 2011-08-20 09:43 +1200
                Re: concatenate variable number of arguments and types to a char * Paul <pchristor@yahoo.co.uk> - 2011-08-19 15:08 -0700
            Re: concatenate variable number of arguments and types to a char * Victor Bazarov <v.bazarov@comcast.invalid> - 2011-08-19 16:14 -0400
              Re: concatenate variable number of arguments and types to a char * Paul <pchristor@yahoo.co.uk> - 2011-08-19 13:54 -0700
                Re: concatenate variable number of arguments and types to a char * Leigh Johnston <leigh@i42.co.uk> - 2011-08-19 22:01 +0100
                Re: concatenate variable number of arguments and types to a char * Paul <pchristor@yahoo.co.uk> - 2011-08-19 14:20 -0700
                Re: concatenate variable number of arguments and types to a char * Paul <pchristor@yahoo.co.uk> - 2011-08-19 14:21 -0700
      Re: concatenate variable number of arguments and types to a char * Paul <pchristor@yahoo.co.uk> - 2011-08-19 11:03 -0700
        Re: concatenate variable number of arguments and types to a char * Leigh Johnston <leigh@i42.co.uk> - 2011-08-19 19:23 +0100
      Re: concatenate variable number of arguments and types to a char * red floyd <no.spam.here@its.invalid> - 2011-08-19 11:13 -0700
        Re: concatenate variable number of arguments and types to a char * Leigh Johnston <leigh@i42.co.uk> - 2011-08-19 19:39 +0100

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