which one do you prefer? python with C# or java?

[Tomasz Rola]

On Fri, 15 Jun 2012, Terry Reedy wrote:

> On 6/15/2012 1:03 PM, Tomasz Rola wrote:
> 
> > Last time I checked, Python didn't have linked lists - arrayed lists are
> > nice, but their elements can't be automatically GC-ed (or, this requires
> > very nontrivial GC algorithm), the easiest way I can think would be
> > replacing them with None manually. I'm not sure if del is
> > performance-nice.
> 
> Python does not come with a linked-list class, but one can easily use tuples
> or lists with two items as linked-list cells. One can optionally wrap such
> cell in a linked-list class. However, if array lists do the job, which they
> usually do, using linked-lists will take more time and space. The problem
> being discussed may be a case where they are useful and make it easier to save
> space.

Yes. I made linked lists in Python few years ago, just to test something. 
At the time Python was my main algorithmic toy, so I couldn't resist.

However, handling the list felt half Pascal-y and half unnatural. Later 
on, I felt I didn't like cramming everything into arrays and switched to 
something else.

> > Also, around the same time, Python couldn't do tail-call,
> 
> Nonsense. A tail call is a call temporally followed by a return. In CPython
> bytecode, it would be a call followed by return. In Python code, it is a call
> spatially preceded by 'return'. Any "return f(whatever)", a common operation
> is a tail call.

Actually I was wrong.

http://code.activestate.com/recipes/474088-tail-call-optimization-decorator/

Now I am intrigued because this code just worked a minute ago, on 2.6.

Given this was written for 2.4, I was wrong.

Definitely something I would like to experiment with a bit. The need for 
adding decorator takes some joy away but it is interesting.

> In practice, should_loop, A, and B will usually be in-line expressions rather
> than calls. There may be additional statements after if, else, and while
> headers. In while_equiv, move b=start into the body. Else is typically omitted
> from the while version, but I prefer it in the recursive version.

You see, I spend quite a lot of time playing with concepts etc. Code 
performance is nice to have, but I prefer to maximize my performance as I 
write something and move on. If I feel (from my own point of view) 
something would be nicer to write with recursion, so be it - even though
 some Common Lisp manual advises to use loops because they are faster. 
Actually, from what I have tested, this not always is true - both 
recursion and loops were comparable speed wise in some simple cases I 
checked. This manual is a bit old, and new compiler had its own say about 
optimisation, maybe that's the truth behind it.

For cases where I really want speed, proper algorithm (if only I can think
it) and compilation rule. If algorithm codes better with loops, this is 
ok. But if it codes better with recursion, this should be ok too, because 
if I feel better while coding it, I make less errors.

> > Even more cool, with lazy evaluation (like in Haskell) one can generate
> > lists on a fly and process them like they were statically allocated.
> 
> Python iterators can do lazy evaluation. All the builtin classes come with a
> corresponding iterator.

This is fine, but I don't mind having more, like the whole language 
supporting the idea of being lazy.

http://stackoverflow.com/questions/265392/why-is-lazy-evaluation-useful

> > Yes, you could also run it in a loop or simulate lazy-eval manually (with
> > yield)
> 
> There is nothing simulated about yield.

Yes, yield is real and not simulated. And one can use it to do tricks with 
how/when Python evaluates/generates/performs. It is nicer than if I had to 
write lazy code in, say, C or Pascal, but it doesn't mean one should only 
use one language rather than choose language according to the task,

> Python mostly does what you tell it to do. You just have to learn how to 
> tell it to do what you want.

Well I believe I have already learnt some of it. I am not using Python on 
a daily basis nowadays, and I am stuck somewhere in 2.x land. To stay in 
this semicurrent state I read this group and, from time to time, some 
shorter PEPs. So I think I can tell Python a thing or two, but at the same 
time I don't want to tell it everything, everytime. :-) I like telling 
things in a language that sounds better, which depends on what I tell, 
actually.

Regards,
Tomasz Rola

--
** A C programmer asked whether computer had Buddha's nature.      **
** As the answer, master did "rm -rif" on the programmer's home    **
** directory. And then the C programmer became enlightened...      **
**                                                                 **
** Tomasz Rola          mailto:tomasz_rola at bigfoot.com             **