|Oscar Wilde, is, of
course, one Ireland's most gifted minters of colorful epigrams...
visiting America for the first time, was asked upon arriving at the New York
Customs House if he had anything to declare, and is said to have replied: I
have nothing to declare except my genius .
-–Oscar Fingal O’Flahertie Wills Wilde (1854-1900) (Wow, when he was my age, he’d been dead for nearly five years.)
|I’ve always thought
this would be nifty / ideal / epigram for a talk on dynamic types. Hence,
here goes nothing.
|Of Type Systems and
customs posts. Goal posts…
|It seems rather
bizarre that one still has to make the case that dynamic types are as
“strong” as static types, but one does. I’d claim they are, in fact stronger.
world type theorists seem like soccer (er, this is Europe so “football”)
coaches who seek to show that their game plan is so foolproof that it can be
conclusively shown that no shot on goal is possible, conceivable, and hence
no goalie is even necessary. In fact, they seek to assert that the game need
not even be played, since victory is certain, and any rational adversary
would capitulate, forfeit in the faceof such claims, of such an irrefutable
demonstration. With a dynamic type
system, we just keep the goalie. Which approach makes YOU feel safer?
|Earlier this year, I
finally came across one of the greatest “classic” papers I’d never read:
“End-to-End Arguments in System Design” by Saltzer, Reed, and Clark. The
end-to-end argument was developed in the realm of internet protocol design.
Succinctly put (and this format allows for no alternative) it argues that
facilities, such as error checking, which one might be tempted to place at
the lower levels of a system or network, might actually be redundant, and
therefore useless as the lower levels, when they must be included in the
upper levels of the system as well.
|We argue that this
argument applies as well to programming language design as it does to
networking. For instance, facilities that some languages provide for
security, protection, synchronization, namespace management, or type checking
must often be re-implemented in applications programs in a variety of
different ways, many at odds with the manner in which these facilities were
provided in these underlying languages. Such duplication raises the question
of why these now redundant facilities need be present in these programming
languages at all.
suggests a simpler, more dynamic approach to programming language design,
based on an end-to-end analysis of the kinds of facilities users really use,
may be better suited to the demands of our clustered, networked, threaded
multi-core 21st world.
live, and breath, function, and yes fail, in a world well beyond our “formal”
logistics train. Real computer science is an empirical, even behavior
science, and not the feeble parody of seventeenth century closed-form
mathematics some in CS make it out to be.
|There are patterns
of programming language design. Objects for lists of states, or zip codes,
these are the types our clients demand. Will the legacy of the reflection
movement be that we get out of their way, and finally give people the tools
to build these as first-class runtime entities?