Re: Overloading member functions, some virtual, some not

From:

David Wilkinson <no-reply@effisols.com>

Newsgroups:

microsoft.public.vc.language

Date:

Sun, 14 Feb 2010 06:09:21 -0500

Message-ID:

<#yqjlYWrKHA.1796@TK2MSFTNGP02.phx.gbl>

Dave wrote:

Hi folks,

Got the following class hierarchy, and am getting a strange compile
error from it:

class RootFinder
{
public:
  virtual ~RootFinder(){}

  double findRoot( const Function1D& func, double guess ) const;
  virtual double findRoot( const Function1D& func, double min, double
max ) const = 0;

private:
  bool findGoodInterval( const Function1D& func, double guess, double&
min, double& max ) const;
};

class BisectionRootFinder : public RootFinder
{
public:
  BisectionRootFinder(){}
  virtual double findRoot( const Function1D& func, double min, double
max ) const;
};

If I then try to use the second class like so:

    BisectionRootFinder rootFinder;
    const double root = rootFinder.findRoot( func, guess );

I get the following compile error on that second line :

    error C2660: 'BisectionRootFinder::findRoot' : function does not
take 2 arguments

I'm not sure why this is happening, as it should be able to find the
non-virtual version of findRoot(...) that is in the base class. I can
coax it to find it by doing the following:

    BisectionRootFinder bisectRootFinder;
    RootFinder& rootFinder = bisectRootFinder;
    const double root = rootFinder.findRoot( func, guess );

and all works fine. But, why do I need to go through that extra step?
Am I declaring something wrong, or is VC just misbehaving? If it
matters, I am using Visual Studio 2008 Express (version 9.0.30729.1
SP)

Them's the rules. Whne the compiler finds a matching name in
BisectionRootFinder, it will not look in the base class for a function with the
correct dignature. I used to think this was odd, but you get used to it.

It will work if you do

class BisectionRootFinder : public RootFinder
{
public:
  using RootFinder::findRoot;
  BisectionRootFinder(){}
  virtual double findRoot( const Function1D& func, double min, double max ) const;
};

However, IMHO, this is not good style. There is really no reason to use the same
name for the two functions here.

--
David Wilkinson
Visual C++ MVP