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Re: C++11 lambdas

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Jerry wrote :

> This works fine:
> 
> int main()
> {
>     std::map<std::string,std::string> parameters;
> 
>     parameters["abc"]="def";
> 
>     std::for_each(parameters.begin(),parameters.end(),
>         [] (std::map<std::string,std::string>::value_type& pair)
>             {std::cout << pair.first << "=" << pair.second << " ";});
> 
>     return 0;
> }
> 
> But g++ 4.6.0 doesn't like it when I change the type of pair in the
> lambda to auto:
> 
> int main()
> {
>     std::map<std::string,std::string> parameters;
> 
>     parameters["abc"]="def";
> 
>     std::for_each(parameters.begin(),parameters.end(),
>         [] (auto pair)
>             {std::cout << pair.first << "=" << pair.second << " ";});
> 
>     return 0;
> }
> 
> So, my question is: why can't it be auto?
> 
> In general I am most interested in why the committee chooses to include
> things or not and I figure there must be a reason this isn't allowed. 
> Or is it allowed and my compiler is just too old?
> 
> Thanks,
> 
> Jerry

Auto knows its type from its initializer. Here there are no initializer. 
It is used for *convenience*. I may be wrong, but I think this is not 
possible because of this.

Here is an example of why : http://ideone.com/pP5jz
/error: parameter declared 'auto'/

-- 
perl -e 's;;{]``*%)}`_^[&)/#%(`&;;\
y;%^)([]/*#&`_{};.\100acghiklmopsz;;print'

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C++11 lambdas Jerry <jerry.jeremiah@gmail.com> - 2011-09-19 15:40 -0700
  Re: C++11 lambdas Lucien Coffe <lcof@nospam.invalid> - 2011-09-20 06:38 +0000
  Re: C++11 lambdas Juha Nieminen <nospam@thanks.invalid> - 2011-09-20 06:41 +0000
    Re: C++11 lambdas Miles Bader <miles@gnu.org> - 2011-09-20 16:57 +0900
    Re: C++11 lambdas Noah Roberts <roberts.noah@gmail.com> - 2011-09-20 08:23 -0700
      Re: C++11 lambdas Juha Nieminen <nospam@thanks.invalid> - 2011-09-21 07:14 +0000
        Re: C++11 lambdas Victor Bazarov <v.bazarov@comcast.invalid> - 2011-09-21 18:25 -0400
  Re: C++11 lambdas ChuanQi Tan <chuanqi.tan@gmail.com> - 2011-10-04 22:04 -0700
    Re: C++11 lambdas Jerry <jerry.jeremiah@gmail.com> - 2011-10-23 15:21 -0700
      Re: C++11 lambdas Miles Bader <miles@gnu.org> - 2011-10-24 17:27 +0900

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