The Tragedy of the Common Lisp, or, Why Large Languages Explode (was: revive let blocks)

Andreas Rossberg rossberg at
Fri Jun 19 12:05:23 UTC 2015

On 19 June 2015 at 10:06, Alexander Jones <alex at> wrote:

> If people are unable to internalize the whole language, then surely we
> need a way to remove cruft and idiosyncracies in it, lest the language
> stagnate beyond repair.
> Removing var, typeof, exotic objects, function declarations, IsNaN, ==,
> enumerable properties, are just a few examples of things we should not be
> frightened to talk about.
> While I don't personally see a need for the proposed let syntax, I think
> that concerns about the language growing uncontrollably should be directed
> at its apparent lack of deprecation strategy, rather than shutting down
> discussion of new ideas that might help us write better programs.

While I agree that the impossibility of deprecating features is a problem
(without a solution in JS), it's also fair to say that deprecation doesn't
really work or help. Take C++ as the obvious example. They do deprecate
occasionally, with difficulties. Yet the language had already blown
complexity out of any sane proportion 25 years ago. Let alone today. Not a
chance that there is a single person who _even remotely_ understands the
full language, and there probably hasn't been one for 3 decades at least.

Deprecation doesn't solve the problem because new cruft typically gets
added orders of magnitude faster than old cruft can ever be removed. That
is true for almost all production languages. Because it's so much easier to
add stuff.

Thus, the only way to keep a language small (if at all) is being extra
careful about adding features. Just about any terrible feature can be
justified by "use cases", but that's insufficient reason to add it.
Especially "convenience" features are a slippery slope. (I could make a
list of ES6 additions that already violate this principle.)

The art in language design isn't what to add, but what to leave out.


> On Thursday, June 18, 2015, Allen Wirfs-Brock <allen at>
> wrote:
>> On Jun 18, 2015, at 12:18 PM, Andreas Rossberg wrote:
>> On 18 June 2015 at 19:26, Benjamin Gruenbaum <benjamingr at>
>> wrote:
>>> This is a mailing list comprised of people who typically have a much
>>> better understanding of the language and its corners than most (even
>>> professional) developers have (and dare I say, are interested in or care
>>> about having). With ES6 the language already got a *lot* bigger and I'd
>>> argue that it's now harder to learn the whole. The tradeoffs were
>>> worthwhile but it's definitely an issue.
>> I dare say that at this point Allen probably is the only person in the
>> world who actually fully knows and understands the complete language. I
>> won't hesitate to admit that I don't. ;)
>> And I occasionally have to go and look up details.
>> Allen
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