[Insight-developers] Best method for a do-nothing return-value function

[M Stauffer (V)]

Hi Luis,
 
After looking into this more, it seems that to be able to inline a functor's function operator, I would have to template a containing class over the functor class.
 
Otherwise, if I were to not template and simply require the user to assign a derived functor to a containing class' member variable of type MyFunctorBaseClass, then it seems the compiler wouldn't know ahead of time the particular functor implementation that's being used, and likely couldn't inline. This then seems like the same issue with inlining a virtual method in a regular class.
 
Does this sound right?
 
Cheers,
Michael 


  _____  

From: Luis Ibanez [mailto:luis.ibanez at kitware.com] 
Sent: Saturday, December 18, 2010 6:22 PM
To: M Stauffer (V)
Cc: ITK-dev-list
Subject: Re: [Insight-developers] Best method for a do-nothing return-value function


Hi Michael,

This call looks reasonable, note however that 
if you declare the function to be "virtual" as you
probably need to do in this case in order to 
achieve polymorphism, then the call to this function
will not be inlined.

The typical option here is to use Functors, if you
want to get both the flexibility of polymorphism,
and the efficiency of inlining.


������ Luis



On Fri, Dec 17, 2010 at 6:09 PM, M Stauffer (V) <mstauff at verizon.net> wrote:


Hi,

I'm not sure how to phrase the subject. I'm creating a function base
class whose "Evaluate", i.e. do-its-thing, method needs to simply return
the input value. Derived classes will modify the value in some way, not
surprisingly.

Is there a more efficient way to implement this than what I have below?
I figure most compilers will actually make this inline, but maybe not
all?

< typename TValue >
class FunctionBase {

...
��inline TValue Evaluate( TValue value ) { return value; }
...

};

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