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Pramod
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 Posted: Thu Feb 16, 2006 3:06 am Post subject: Typedef |
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Hi,
I am new to C++ . I was trying to compile following Class which just
has a map from integer error code to error description. I am not sure
of the complier error.
Why compiler flags error for typedef present in *private* area of the
class. If I move the typedef to *public* are it complies fine.
RegExp.h
--------------
class RegError {
public:
RegError( int ErrorCode ) ;
const std::string what ( ) ;
private:
int regerror;
typedef std::map< int , std::string > ErrorMap;
static void InitializeErrorMap ( );
static ErrorMap RegExpError;
};
RegExp.C
-----------------
static RegError::ErrorMap RegExpError;
=================================================================
Compiler g++
------------------
RegExp.h:16: error: 'typedef class std::map<int, std::string,
std::less<int>, std::allocator<std::pair<const int, std::string> > >
RegError::ErrorMap' is private
RegExp.C:4: error: within this context
Compiler aCC
---------------
Error 182: "RegExp.C", line 4 #
"std::map<int,std::basic_string<char,std::char_traits<char>,std::allocator<char>
| Quote: | ,std::less<int>,std::allocator<std::pair<const
int,std::basic_string<char,std::char_traits<char>,std::allocator<char
RegExpError" cannot access private member "typedef |
std::map<int,std::basic_string<char,std::char_traits<char>,std::allocator<char>
| Quote: | ,std::less<int>,std::allocator<std::pair<const
int,std::basic_string<char,std::char_traits<char>,std::allocator<char
RegError::ErrorMap". |
static RegError::ErrorMap RegExpError;
^^^^^^^^^^^^^^^^^^
Thanks in advance.
Pramod
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Guest
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| Posted: Sat Feb 18, 2006 1:06 am Post subject: Re: Typedef |
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Pramod wrote:
| Quote: | RegExp.C
-----------------
static RegError::ErrorMap RegExpError;
|
remove "static":
RegError::ErrorMap RegExpError;
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werasm
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| Posted: Sat Feb 18, 2006 1:06 am Post subject: Re: Typedef |
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Pramod wrote:
| Quote: | Hi,
Why compiler flags error for typedef present in *private* area of the
class. If I move the typedef to *public* are it complies fine.
|
IMHO this should not make a difference as you are only providing a
definition for the static member. Therefore you must be able to qualify
the type under scrutiny. I did not notice
....
#include <map>
#include <string>
....
in your code.
| Quote: |
RegExp.h
--------------
class RegError {
public:
RegError( int ErrorCode ) ;
const std::string what ( ) ;
private:
int regerror;
typedef std::map< int , std::string > ErrorMap;
static void InitializeErrorMap ( );
static ErrorMap RegExpError;
};
RegExp.C
-----------------
static RegError::ErrorMap RegExpError;
|
<static> should not be used here...
RegError::ErrorMap RegError::RegExpError; //should do!
You forgot to qualify the class member RegExpError, therefore you did
not provide a definition for the static member but actually
declared/defined a global member called RegExpError. Good thing you
made the typedef private, else the code would have done something other
than you've expected  .
Werner
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Audison.Athena
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| Posted: Sat Feb 18, 2006 1:06 am Post subject: Re: Typedef |
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because access control applies to name, if access control is applied to
a typedef name, only the accessibility of the typedef name itself is
considered. The accessibiliy of the entity
of the entity referred to by the typedef is not considered.
so the access control is only apply to the typedef name "ErrorMap"
itself, but not apply to the entity "std::map< int , std::string >"
referred to by "ErrorMap". so you aught to put the typedef declaration
to public field.
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Guest
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| Posted: Sat Feb 18, 2006 2:06 am Post subject: Re: Typedef |
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|
Pramod wrote:
| Quote: | Hi,
I am new to C++ . I was trying to compile following Class which just
has a map from integer error code to error description. I am not sure
of the complier error.
Why compiler flags error for typedef present in *private* area of the
class. If I move the typedef to *public* are it complies fine.
RegExp.h
--------------
class RegError {
public:
RegError( int ErrorCode ) ;
const std::string what ( ) ;
private:
int regerror;
typedef std::map< int , std::string > ErrorMap;
static void InitializeErrorMap ( );
static ErrorMap RegExpError;
};
RegExp.C
-----------------
static RegError::ErrorMap RegExpError;
|
Similarly,
static RegError::ErrorMap someOtherErrorMap;
wouldn't compile because RegError::ErrorMap is a private type.
try, instead:
static RegError::ErrorMap RegError::RegExpError;
see the missing RegError::?
Tony
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Heinz Ozwirk
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| Posted: Sat Feb 18, 2006 5:06 am Post subject: Re: Typedef |
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"Pramod" <pramod.shimoga (AT) gmail (DOT) com> schrieb im Newsbeitrag
news:1140025917.257521.116880 (AT) g14g2000cwa (DOT) googlegroups.com...
| Quote: | Hi,
I am new to C++ . I was trying to compile following Class which just
has a map from integer error code to error description. I am not sure
of the complier error.
Why compiler flags error for typedef present in *private* area of the
class. If I move the typedef to *public* are it complies fine.
|
If something is defined in the private section of a class, it is private and
must not be used outside its class. If it is defined in the public section,
it is public and may be used everywhere. That's what public and private have
been invented for. So, of cause you get an error if you try to use something
private outside its class, and of cause this error goes away when you make
it public.
| Quote: |
RegExp.h
--------------
class RegError {
public:
RegError( int ErrorCode ) ;
const std::string what ( ) ;
private:
int regerror;
typedef std::map< int , std::string > ErrorMap;
static void InitializeErrorMap ( );
static ErrorMap RegExpError;
};
RegExp.C
-----------------
static RegError::ErrorMap RegExpError;
|
This defines a global variable of type RegError::ErrorMap, and since
ErrorMap has been declared private in RegError you cannot use that type
outside the class. Probably that should have been a definition for
RegError::RegExpError, but such a definition should be written as
RegError::ErrorMap RegError::RegExpError;
HTH
Heinz
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Marco Wahl
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| Posted: Sat Feb 18, 2006 5:06 am Post subject: Re: Typedef |
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"Pramod" <pramod.shimoga (AT) gmail (DOT) com> writes:
| Quote: | Why compiler flags error for typedef present in *private* area of the
class. If I move the typedef to *public* are it complies fine.
^^^^^^^^ |
Hehe... 'Comply' is a fresh alternative to 'compile'.
Typedefs in the *private* area are not accessable from the outside (if
you don't use 'friend'). That's simply a part of the definition of
the C++-language. It's the same with member-variables and
member-function.
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viscroad
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| Posted: Sat Feb 18, 2006 5:06 am Post subject: Re: Typedef |
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private class member can't invoke out the class scope.
"typedef std::map< int , std::string > ErrorMap;" is a private class
member, so you can't use it out of the class scope.
only the class member and friend member can use the *private* member.
| Quote: | Why compiler flags error for typedef present in *private* area of the
class. If I move the typedef to *public* are it complies fine.
you put it into *public* area, so, we can use it. |
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jeroen
Guest
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| Posted: Sat Feb 18, 2006 5:06 am Post subject: Re: Typedef |
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Don't have the time to really check this out, but to initialise a
static member of a class you'll have to name the class too, like this
(Note that RegError is mentioned twice, once for the type and once
again for the name of the member-var):
RegExp.C
--------
static RegError::ErrorMap RegError::RegExpError;
In your code you tried to create a new static variable of a private
type, which is not allowed.
Regards,
Jeroen.
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Ulrich Eckhardt
Guest
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| Posted: Sat Feb 18, 2006 5:06 am Post subject: Re: Typedef |
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Pramod wrote (in short):
| Quote: | class RegError {
private:
typedef std::map< int , std::string > ErrorMap;
static ErrorMap RegExpError;
};
static RegError::ErrorMap RegExpError;
|
Here, you try to create an ErrorMap called RegExpError (i.e. in the global
namespace) and with static linkage. This has nothing to do with the equally
named object inside class RegError!
What you want is probably to define the latter, the syntax for that is
RegError::ErrorMap RegError::RegExpError;
cheers
Uli
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