dolfin team mailing list archive

[Ola Skavhaug <skavhaug@xxxxxxxxx>]

On Mon, Sep 7, 2009 at 9:21 AM, Ola Skavhaug<skavhaug@xxxxxxxxx> wrote:
> We've run into problems since only GenericMatrix provides the default
> argument for norm type. Swig does not like this and omits generating a
> constructor for the derived types. According to
> https://www.securecoding.cert.org/confluence/display/cplusplus/OBJ04-CPP.+Prefer+not+to+give+virtual+functions+default+argument+initializers
> virtual function should not provide default arguments at it tends to
> "defeat polymorphism":
>
>
> class Thing {
>  public:
>    virtual ~Thing();
>    virtual void doItNTimes( int numTimes = 10 );
>    virtual void doItThisHigh( double howHigh = 1.0 );
>    // ...
> };
> class MyThing : public Thing {
>  public:
>    void doItNTimes( int numTimes );
>    void doItThisHigh( double howHigh = 2.2 );
>    // ...
> };
>
> MyThing *mt = new MyThing;
> Thing *t = mt;
> t->doItNTimes(); // default of 10
> mt->doItNTimes();  // compile time error!
> t->doItThisHigh(); // default of 1.0!
> mt->doItThisHigh(); // default of 2.2
>
>
> Is this the intended behaviour anyhow?
>
> This is the proposed solution:

Ouch, this was another, bad solution actually :)

The proposed solution (from the link above) is roughly like this:

class Base
{
   public:
      void foo(double bar = 1.0) { foo_impl(bar); }
   protected:
      virtual void foo_impl(double bar);
};

class Sub: public Base
{
   protected:
      virtual void foo_impl(double bar);
};


Sorry about that...

Ola

> static double const minimumHeight = 1.0;
> // ...
> namespace XYZ {
> class Thing {
>  public:
>    virtual ~Thing();
>    virtual void doItThisHigh( double howHigh = minimumHeight );
>    // ...
> };
> }
> // ...
> namespace XYZ {
> static double const minimumHeight = 2.2;
> class MyThing : public Thing {
>  public:
>    void doItThisHigh( double howHigh = minimumHeight );
>    // ...
> };
> }
>
>
> Resolving this issue also means getting the Python interface back on track.
>
> Ola
>
>
> --
> Ola Skavhaug
>



-- 
Ola Skavhaug