checking if a list is empty

[Chris Rebert]

On Thu, May 12, 2011 at 11:46 PM, rusi <rustompmody at gmail.com> wrote:
<snip>
> The boolean domain is only a 100 years old.
> Unsurprisingly it is not quite 'first-class' yet: See

It is nowadays. Every halfway-mainstream language I can think of has
an explicit boolean datatype. Heck, as of C99, even C has one now. I
conjecture the only languages still lacking one are exotic
niche/fringe languages. I would be interested to see a counterexample.

> http://www.cs.utexas.edu/users/EWD/transcriptions/EWD10xx/EWD1070.html
> [Lifted from http://c2.com/cgi/wiki?EqualVsTrueFalse ]
>
> ----------------------------
> "In retrospect, one might be tempted to regard the introduction of
> something as simple as the boolean domain as a minor invention, but I
> think that that would be a grave mistake: it is a great invention
> because, being so simple, it is such a powerful simplifier. It is of
> the same level as the introduction of natural numbers, which enabled
> us to add 3 to 5, regardless of whether we are adding apples or
> pears."
>
> "George Boole made a radical invention, so radical, in fact, that now,
> more than a century later, the scientific community has not absorbed
> it yet. (To stay with the metaphor: officially, boolean expressions
> may have reached the status of first-class citizens, in practice —
> because old habits and prejudices die hard— they are still the victims
> of discrimination.) Let me give you a few examples."
>
> "In the programming language FORTRAN, as conceived a century after
> Boole published his invention, boolean expressions are allowed, but
> there are no boolean variables! Their introduction into programming
> had to wait until the design of ALGOL 60."
>
> ------------------------
> So, M Harris problem is that python could almost be a language for the
> 'masses' (whatever that might mean) were it not for warts like "l not
> is empty" is shorten-able to just "l"

One language's wart is another language's idiom. And I think the
irrational hate towards syntactically-significant indentation is by
far a much larger barrier to "mass" adoption of Python; C++ has some
features that are at least (if not more) subtle/unobvious than
Python's __bool__(), yet it still enjoys "mass" use.

> Dijkstra's problem (paraphrased) is that python, by choosing the
> FORTRAN alternative of having a non-first-class boolean type, hinders
> scientific/mathematical thinking/progress.

Python has *not* chosen the Fortran alternative; *it has a first-class
Boolean type*, namely bool. This line of argument thus fails.
The fact that other types are implicitly coercible to bools doesn't
make `bool` itself any less first-class.

It is also ironic that one of the projects that exploits Python's
flexible typing regarding normally-Boolean operators is a scientific
one (NumPy).

Cheers,
Chris
--
http://rebertia.com