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rtrimws: can't compile in g++

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  rtrimws: can't compile in g++ eric <cneric12lin0@gmail.com> - 2011-07-06 22:30 -0700
    Re: rtrimws: can't compile in g++ Miles Bader <miles@gnu.org> - 2011-07-07 15:11 +0900
      Re: rtrimws: can't compile in g++ eric <cneric12lin0@gmail.com> - 2011-07-06 23:26 -0700

#7563 — rtrimws: can't compile in g++

Dear advanced c++ programers:

  I copied and tested a piece simple Trimming string code from book c+
+ cookbook in chapter4, section2
Example 4-4:Trim trailing whitespace.  You can download and try it by
yourself.
-------------------------------------------------
http://examples.oreilly.com/9780596007614/
-------------------------------------------------------------------
in my g++ 4.5.2, compiler reponse
--------------------
4-4.cpp: In function ‘void rtrimws(std::string&)’:
4-4.cpp:21:21: error: too many arguments to function ‘void
rtrimws(std::string&)’
4-4.cpp:20:6: note: declared here
------------
according to the book, all book example code is compiled success in
Visual C++ compiler
so, please help
Eric

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#7564

eric <cneric12lin0@gmail.com> writes:
> --------------------
> 4-4.cpp: In function ‘void rtrimws(std::string&)’:
> 4-4.cpp:21:21: error: too many arguments to function ‘void
> rtrimws(std::string&)’
> 4-4.cpp:20:6: note: declared here
> ------------

The problem seems to be that there are multiple overloaded versions of
"isspace"[*], and the compiler doesn'tn know which one you want.

Changing the function that contains line 21 to the following seems to
make it work (though I dunno if it's the best solution):

   // Overloads to make cleaner calling for client code
   void rtrimws(string& s) {
     rtrimws (s, static_cast<int(&)(int)> (isspace));
   }

[I added the cast to "int(&)(int)" to force it to choose a particular
variant of isspace...]


[*] One is the usual "int isspace(int)", but there's _also_ this:

  template<typename _CharT>
    bool
    isspace(_CharT, const locale&);


-Miles

-- 
Acquaintance, n. A person whom we know well enough to borrow from, but not
well enough to lend to.

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#7565

On Jul 6, 11:11 pm, Miles Bader <mi...@gnu.org> wrote:
> eric <cneric12l...@gmail.com> writes:
> > --------------------
> > 4-4.cpp: In function ‘void rtrimws(std::string&)’:
> > 4-4.cpp:21:21: error: too many arguments to function ‘void
> > rtrimws(std::string&)’
> > 4-4.cpp:20:6: note: declared here
> > ------------
>
> The problem seems to be that there are multiple overloaded versions of
> "isspace"[*], and the compiler doesn'tn know which one you want.
>
> Changing the function that contains line 21 to the following seems to
> make it work (though I dunno if it's the best solution):
>
>    // Overloads to make cleaner calling for client code
>    void rtrimws(string& s) {
>      rtrimws (s, static_cast<int(&)(int)> (isspace));
>    }
>
> [I added the cast to "int(&)(int)" to force it to choose a particular
> variant of isspace...]
>
> [*] One is the usual "int isspace(int)", but there's _also_ this:
>
>   template<typename _CharT>
>     bool
>     isspace(_CharT, const locale&);
>
> -Miles
>
> --
> Acquaintance, n. A person whom we know well enough to borrow from, but not
> well enough to lend to.

Thanks your suggestion, Eric

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