Re: Is strong typing worth the cost?

[Jim Rogers <jimmaureenrogers@worldnet.att.net>]

dmjones wrote:

> Marc,
> 
> 
> Why?  Can you prove to me that the benefits will be greater
> than the costs?
> 
> Why am I asking for this evidence?  I am working on a detailed
> analysis of C that includes material on coding guidelines.
> I have set myself the target of basis these guidelines on
> empirical evidence.  I am a fan of strong typing.  However,
> unless I can find any evidence to the contrary, the most I
> can say at the moment is "some people think ...".
> 


What costs are you seeing?

Seriously, any software that reports itself as safe and
correct must perform a significant amount of what the old
COBOL programmers call data editing. It must verify that the
data is correct in all phases of the program. Weakly typed
languages such as C do not avoid this problem. C simply
delegates all such responsibility to the application
programmer. Ada, on the other hand, allows the application
programmer to supply important information, such as the minimum
and maximum values for a scalar type, and then lets the
compiler generate the range checking.

Range checking always requires someone to do the coding.
Ada has put that burden on the compiler developer. C puts it
on the application developer. For the application developer this
makes coding in C more expensive than coding in Ada.

C complicates the problem by its extensive use of implicit
numeric convrsions. The C compiler is not allowed to object if
you assign an int to a double. In all cases, such assignments
are dangerous. C insists the danger does not exist because a
double can always represent all values representable in an int.
The problem is that you can be assigning an AppleCount to a
WeightOfScrapIron. Strong typing can flag the danger of such
assignments, forcing you as the programmer to review your
program. Weak typing gives you no help. You are left with the
need to carefully test all possible value combinations for your
code, an impossible task for any non-trivial program.

Jim Rogers