Re: Is strong typing worth the cost?

[Preben Randhol <randhol+abuse@pvv.org>]

On Fri, 03 May 2002 02:45:56 GMT, dmjones wrote:
> All,
>  
>> I have been trying to locate evidence that the cost of the use
>> of strong typing is repaid by a greater benefit.
> 
> I have been following up on the references posted here (thanks all).
> 
> Figure 4 of "Impact of Ada and object-oriented design in the
> flight dynamics division of Goddard Space Flight Center",
> SEL-95-001 shows a graph of "total types per statement" vs
> time (a five year period).  The increase is claimed to be
> due to an increase in use of strong typing.

As I understand the text and Figure it shows how Ada developers were
using more strong typing and generic and less tasking and shorter
package sizes over the years from 1985 to 1993. So they were starting to
utilise the features of the language.

> How is "total types per statement" measured?
> Is it an average of the number of types appearing in the
> same statement?

It says earlier that the statement count is "the number of logical
statements and declarations". It further says that since 1985 the number
of lines per statement for FORTRAN increased from 2.5 to 5 due to
commenting, where for Ada it went from 6 to 3 as more of the Ada coding
style was used. So it may look like strong typing is doing much of the
commenting for you, but this is just a guess as I haven't seen the
report referred to either. But at least I think it is a fair
interpretation.

But I think that the gains of strong typing are

   reduction in debugging time, more errors are found during compilation
   more information can be retrieved, ranges etc...
   leads to a more self-commenting source code.
   makes maintainability easier

though I have no scientific proof. Neither do I see any proof saying
that weak typing is better in any way.

Are there really a lot of projects out there where maintainability isn't
an issue? I can understand that software companies may not care about
this, because if they have to rewrite the entire program in order to
give the customer a new version with additional features/removal of
errors, they would use more time and get more paid. But if the customers
don't take this into account, then I don't understand. Given the history
of Y2K, it shows clearly IMHO that maintaining the system you have is
done to a great extent even if the customer thought he would switch to a
new superduper system in the near future. I hope that the times were
customers review software engineers as sort of witch-doctors of the
village are over. :-) There are two much magic mumbo-jumbo in the air
and I for one thinks that bug is a euphemism for error. ;-) 

OK enough on this, I'll go back to do some more strong typed coding and
code reading. :-)

Preben
-- 
�There are three things you can do to a woman. You can love her, suffer
 for her, or turn her into literature.�  - Justine, by Lawrence Durrell