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RE: dynamic vs. static typing
Paul F. Dietz wrote:
> Anton van Straaten wrote:
> > > > Without early typechecking, the proportion of type errors which
> > > > manifest during testing and at runtime rises significantly -
> > > > and often, their nature isn't as clearly identified, so they
> > > > take longer to track down. Looking at this in terms of what
> > > > percentage they are of all possible errors is misleading at best.
> > >
> > > But is there any evidence to support the contention that the putative
> > > savings in debugging time exceeds the extra design and coding cost?
> > Is there any evidence to support the above implied contention that
> > an *extra* design and coding cost exists? The costs (in terms of
> > time) with DT systems may simply be shifted to later in the
> > development cycle.
> I would like to know if your statement about savings was actually
> evidence-based, or merely a statement of dogma or prejudice.
The statement of mine quoted originally, reinserted above, makes the
1. Without early typechecking, the proportion of type errors which manifest
during testing and at runtime rises significantly.
2. Often, the nature of those type errors isn't identified as clearly during
testing or at runtime as it would be by a type-checker, so they take longer
to track down.
3. Looking at these errors in terms of what percentage they are of all
possible errors is misleading at best.
(1) is a trivial truth. (3) is a criticism of an earlier claim, the
rationale for which can be found in books like "How to Lie with Statistics".
(2) is based on evidence I've encountered during development in both DT and
ST languages, over many years, including experience with other developers
that I've worked with, in both development and mentoring capacities. I
don't consider it a statement of dogma or prejudice.
Repeating myself, I'm not arguing that ST is the best choice in all cases.
But it has benefits which many people, including myself, have experienced.
We also know it's possible to provide more of those benefits in DT
languages. What I've mostly been arguing against is the rejection of static
typechecking without exploring or understanding what that can mean, beyond
what e.g. C++/Java or even ML/Haskell provide, and especially when that
rejection seems to be based on misconceptions about what static typechecking
is capable of.