Re: programming guidelines, prefer free functions

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-08-17 13:41:33

--- In boost_at_[hidden], Gary Powell <Gary.Powell_at_s...> wrote:
> Another reason to use free functions vs member functions:
> 
> o) It can reduce compile time dependencies, if you place the free 
functions
> in a separate include file. Then things which require
> access to the object include only the definition.h and things which
> use the free functions include the objectUtility.h file.

There are ways to reduce compile time dependencies beyond just using 
free functions.  I don't see this as a real argument.

> --------------------------
> Regarding Jeremy's example if you don't own the interface/code to 
> Joe::Vector or suzy::vector_add adding a member function is not an 
option.
> i.e. Using third party software. If you go ahead and modify the 
include
> files to joe's vector, whenever you get an update you are required 
to repeat
> this modification. Ick!

Then wrap it instead.  Jeremy's example fails to illustrate anything, 
because template specialization could have been used instead.  Or an 
adapter class could have been used.  All of these require a lot of 
intimacy with suzy::vector_add, however, which calls into question 
whether any of them should be employed or if we should simply start 
from scratch here.  I guess I still don't see any issue, or any 
improvement by using free functions.
 
> The fix by specialization takes care of this. (Also it can be used 
to
> generate a "size" function if none exists at all in Joe::vector)

Good luck adding a "size" function if none exists in Joe::vector, 
since such a method would require access to state information that 
shouldn't be directly exposed in the class any way.
 
> The issue is a that a class should provide no more member functions 
than are
> necessary. Just what that minimum set is of course open to 
discussion and
> endless debate.

Now this I will agree with.  However, it does not lead to "prefer 
free functions over member functions" in my mind.

Bill