On 19 December 2011 22:28, Nathan Rice <nathan.alexander.rice@gmail.com> wrote:
On Mon, Dec 19, 2011 at 3:37 PM, Joshua Landau
<
joshua.landau.ws@gmail.com> wrote:
> ...or we could just extend Pep 225 (deferred) with "~." so we have "['a',
> 'b', 'c']~.upper()" [syntax debatable]. You don't get the type-checking but
> that seemed more of a problem to me, as I'm not a real duck.
solutions to problems with overloaded operators are hard to google
for. If the method calls were aliased, google searches would be
easier and less experienced users wouldn't have to worry about
wrestling with operator overloading.
The thing is, "listofstrings.method()" is less obviously elementwise than "listofstrings~.method()", especially if "~" becomes the default elementwise character. So I have to disagree. Additionally, "listofstrings~.method()" is easy to paste into an interpreter, and should quickly yield enlightenment. I don't see that as a valid argument.
That being said, I think
elementwise operators are a great idea in a numeric/scientific
context.
But not always in the same case as your broadcasting idea? The elementwise operator is far more general, so I'd say it has a more general use-case in response. Only a fraction of my code is of the "numeric/scientific" type, and I'd lap up elementwise operators.
There are of course both pros and cons to having type declarations. I
know that people do not like to be limited by a lack of foresight in
their predecessors; I have run into unreasonable interface/type
specifications and annoyances with private/protected variables in
Java and I would never want to see that infiltrate Python. I think
what I am trying to sell here is more akin to metadata than static
types. People should be able to basically keep doing what they are
already doing, but have a reasonable mechanism to provide additional
object metadata in a standard way that is easily accessible by
downstream consumers. That gives you a lot of the upsides of type
declarations while staying Pythonic.
The thing is... what? This isn't a criticism. I'm genuinely lost as to what you mean. I lost you on the "metadata" part. In what way is this metadata, and in turn not typing? Can you do:
foo = "a b".split()
foo[1] = 1
If you can, then this whole idea should really be generalised more, preferably to the elementwise operator level, as it's got no real type constraints. If you can't, then how is it not typing? Again, this is a genuine question. I'm home-taught, so please don't expect me to know the lingo :P.
I actually love the idea of typing when done well. I've just started Haskell (quite a shock to my Python'd brain) and I've thoroughly enjoyed its type system. I just think that it has no place in python. It only works in Haskell because Haskell is built on it, and types can't go a-changin' (nor can values, for that matter). In python, this sort of system will mean that typed code/arrays/iterators will severely grind with untyped code/values/arrays/iterators.
Someone defines a 'typed collection or iterator', to paraphrase the title. Someone else makes a goose-that-looks-like-a-duck, but doesn't have a beak. With an untyped system - such as the current method or an elementwise operator - that's fine as you just want it swim, but with your typed container something has to go wrong! Either it crashed, which is anti-duck-typing, or it falls back down, in which case you end up reverting everything to the old method anyway.
Haskell gets around this by having both types and 'things that implement things' and so could do this because it knows what everything implements. But in python we don't know, and won't until all our dusty code is rewritten. I apologise for using a language I've just started to learn as a reference, but that's the best reference I've had.
*I really should check this, but it's late and I'm tired. If I've said the same thing twice or rambled on about hexagonal motorised paintings for too long, blame my cat...*
Maybe a better option than having a "type contract" base for
homogeneous collections is to give objects a metadata namespace with a
loose schema, and declare it there? As long as you could provide the
metadata at object creation time you would still get all the same
benefits, and it would avoid potentially overworking the class/mixin
concept.
> Your example:
> my_string.split("\n").capitalize().join_items("\n")
> to
> "\n".join(my_string.split("\n")~.capitalize())
>
> And personally I like "string.join(lst)" over "lst.join_with(string)"...
Of course, everyone has their own preferences; having a very small set
of internally consistent ways to do something rather than just one way
is good for this reason.
Nathan
Before anyone gets too many ideas about what is and isn't:
>>> str.capitalize("ABCDEFGH")
'Abcdefgh'
Remember that these are predominantly lowercasing actions :P