Unification of Methods and Functions

[James Moughan]

David MacQuigg <dmq at gain.com> wrote in message news:<47cna0d9cbkfr2vovdhs692cklnmu0oo6h at 4ax.com>...
> On 17 May 2004 20:11:44 -0700, moughanj at tcd.ie (James Moughan) wrote:
> 
> >David MacQuigg <dmq at gain.com> wrote in message news:<4ka7a0t585802d81i417j5ufmrdjbq6hei at 4ax.com>...
>  
> >> We need to make a distinction between users and programmers in our
> >> expectations of what kind of errors they will make.  Users only need
> >> to *read* a class definition and understand what it does.  Programmers
> >> are the group that needs to remember to add a call to the superclass
> >> when they write a new class.
> >> 
> >> I am a user of the Qt Toolkit, but I would not attempt to add a class
> >> to their existing hierarchy.  Nor would I expect Trolltech to provide
> >> me with some kind of robust class-generating function that was
> >> guaranteed to generate an error-free class at any point in their
> >> hierarchy I might chose to insert it.
> >
> >If you're writing code, you're writing it to be modified at some
> >point, unless it's a few lines-long script.  If the modifications are
> >made by someone else then they will reasonably expect that the code
> >doesn't contain implicit deathtraps, like non-local data.
> 
> The trade-off, in the case of _numAnimals is: Do we want a simple
> program with instant display of this number, or a more complex program
> that scans the entire hierarchy to re-create the total every time it
> is needed.
> 
> There is an analogy in the netlisting programs used in circuit design.
> Netlisting a big design is a time-consuming operation, so each cell is
> netlisted when it is saved.  When the design is simulated, there is a
> quick check of the time-stamps on the entire hierarchy, to make sure
> all of the incremental netlists are up-to-date.  One could argue that
> somehow the time-stamps could get out-of-sync (incorrect clock setting
> on a client machine, etc.).  Yet nobody says that not netlisting the
> entire design every time is bad programming.
> 
> It's always a compromise.  Robustness is never absolute.

All true; there are certainly times when you need to store complex
calculations, otherwise we'd all be programming in Haskell.

However, there are different ways to achieve the same result.  Some
would be transparent and relatively easy to debug, like storing the
number at a container-instance level.  The particular way it is done
in Animals_2 is, IMO, one of the less desirable alternatives,
especially as a pattern to teach students.

Jam

> 
> -- Dave