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From: diamond@jit345.swstokyo.dec.com (Norman Diamond)
Newsgroups: comp.object,comp.lang.misc
Subject: Re: Run-time Type Errors in Smalltalk (was Re: blip (was...))
Message-ID: <1991Apr9.084722.14823@tkou02.enet.dec.com>
Date: 9 Apr 91 08:47:22 GMT
References: <1991Apr8.085602.5082@tkou02.enet.dec.com> <3288@charon.cwi.nl>
Sender: usenet@tkou02.enet.dec.com (USENET News System)
Reply-To: diamond@jit345.enet@tkou02.enet.dec.com (Norman Diamond)
Organization: Digital Equipment Corporation Japan , Tokyo
Lines: 35

In article <3288@charon.cwi.nl> guido@cwi.nl (Guido van Rossum) writes:

>Python, which has dynamic typing, was strongly inspired by ABC, which has
>static typing.  In other aspects, the two are much more similar then
>your average pair of statically/dynamically typed languages: both are
>interactive and interpreted, and have large runtime packages that
>replace core dumps by understandable error messages (really exceptions
>for Python).
[...]
>Were all else kept equal, I'd still prefer dynamic typing.

Dynamic typing indeed makes some things easier, as Mr. Rossum explained.
It is nice to see real evidence for a change.

Anyway, there is a middle ground which has also been suggested by a few
others, and which some languages (e.g. Eiffel, and certain constructs in
C++) come close to providing anyway.  Perhaps some new terms would help
explain this.  Just as type and class have come to mean different things,
perhaps dynamic classing vs. static classing should be recognized.  With
static classing, a type inference system could determine, or a programmer
could specify, that a variable inherits certain known messages, though the
precise type need not be known statically.  I expect that static classing
will have a lot more use than static typing.

I would not try to ram either static typing or static classing down
anyone's throat, but both can be used by disciplined developers and
maintainers to catch some errors early.  Although it cannot catch all
errors, it certainly helps.  Part of the folklore of software engineering
is the magnitude of increase in costs as error detection is delayed.
--
Norman Diamond       diamond@tkov50.enet.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.
--
Norman Diamond       diamond@tkov50.enet.dec.com
If this were the company's opinion, I wouldn't be allowed to post it.