Unification of Methods and Functions

[David MacQuigg]

On 19 May 2004 22:27:05 -0700, moughanj at tcd.ie (James Moughan) wrote:

>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.

I'm still waiting for that one simple example that you say will do it
all, and do it right.

-- Dave