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Re: mutable v's non const

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On 07/10/11 08:58 PM, Paul wrote:
>
> "red floyd"<no.spam.here@its.invalid>  wrote in message
> news:ivb9mo$grv$1@dont-email.me...
>> On 7/9/2011 10:15 AM, Paul wrote:
>>> Hi groupies.
>>>
>>> What is the meaning of the "mutable" word in C++ circles?
>>> Mutable apparently means "it can change". So why are the terms "mutable"
>>> and "non-mutable" used instead of const and non-const and in what way
>>> are they different?
>>
>> A mutable class member may be modified even if the object is const.
>>
>> e.g.:
>>
>> class Example {
>>     public:
>>        void good() const {
>>           mutable_int = 7;
>>        }
>>        void bad() const {
>>           non_mutable_int = 7; // ERROR
>>        }
>>        Example() :
>>          mutable_int(0), non_mutable_int(0)
>>        {
>>        }
>>    private:
>>       mutable int mutable_int;
>>       int non_mutable_int;
>> };
>>
> Thanks for the example.
>
> Why would you make such a function const in the first place?
> If its not const why mark it as const?

So it can be called on a const instance of an Example.

-- 
Ian Collins

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Thread

mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-09 18:15 +0100
  Re: mutable v's non const red floyd <no.spam.here@its.invalid> - 2011-07-09 21:26 -0700
    Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-10 09:58 +0100
      Re: mutable v's non const Ian Collins <ian-news@hotmail.com> - 2011-07-10 21:16 +1200
      Re: mutable v's non const Daniel Weber <usenet@daniel-weber.eu> - 2011-07-10 12:41 +0200
        Re: mutable v's non const Leigh Johnston <leigh@i42.co.uk> - 2011-07-10 14:01 +0100
          Re: mutable v's non const Miles Bader <miles@gnu.org> - 2011-07-10 23:35 +0900
          Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-10 16:15 +0100
        Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-10 16:12 +0100
          Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-10 16:21 +0100
            Re: mutable v's non const Werner Erasmus <werasm@gmail.com> - 2011-07-10 21:55 +0200
              Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-10 21:45 +0100
                Re: mutable v's non const Leigh Johnston <leigh@i42.co.uk> - 2011-07-10 22:03 +0100
                Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-10 23:37 +0100
                Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-11 17:43 +0100
                Re: mutable v's non const Leigh Johnston <leigh@i42.co.uk> - 2011-07-11 17:48 +0100
                Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-11 18:04 +0100
                Re: mutable v's non const Leigh Johnston <leigh@i42.co.uk> - 2011-07-11 18:14 +0100
                Re: mutable v's non const "Paul" <pchristor@yahoo.co.uk> - 2011-07-11 18:32 +0100
                Re: mutable v's non const Oliver Jackson <chexmofo@hotmail.com> - 2011-07-12 12:32 -0700
                Re: mutable v's non const "io_x" <a@b.c.invalid> - 2011-07-12 09:42 +0200
      Re: mutable v's non const Werner Erasmus <werasm@gmail.com> - 2011-07-10 17:17 +0200
      Re: mutable v's non const Juha Nieminen <nospam@thanks.invalid> - 2011-07-12 06:04 +0000
    Re: mutable v's non const "MikeP" <mp011011@some.org> - 2011-07-15 00:50 -0500

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