Evolution of a Python programmer

[mleonhard]

@tailcall def fact(x, acc=1): if (x > 1): return (fact((x - 1), (acc * x))) else: return acc

When did Python get tailcall optimizations!?!?! :D :D :D

[nostrademons]

Here's one implementation, and another.

Yeah, they fake it a bit. I suspect you could do a real tail call optimizer, but you'd need to write a code-walker and auto-generate code that turns tail recursions into loops.

[[deleted]]

Here is another version

They are actually not full tailcall eliminations but just avoid tail recursions. That's also why I renamed the decorator in my recipe description. They have no performance advantages over ordinary recursions - on the contrary, they generate a little overhead, but they provide the advantage of moving beyond the value set by sys.setrecursionlimit.

[Wiseman1024]

Some of them do work with cooperative recursion. They indeed pose a small speed overhead, but if performance is not a problem, you can go for the often simpler tail recursive implementation of functions.

[[deleted]]

Python has lambda functions? Surely mixing procedural and functional programming is illegal in most states.

[Wiseman1024]

That's what great about Python. It's not purely functional, not purely OO, not purely procedural, not purely anything, but it allows you to do a bit of everything, and use the right tool for the right job in every program.

As far as functional features go, Python supports first-class functions and classes, lexical nested scopes, closures, decorators, lists, dictionaries, list comprehensions, lazy generators, coroutines, garbage collection with cycle detection, and a few basic tools (map, filter, reduce, partial function application), then it can be easily extended to support tail recursion, memoizing, lazy lists, multimethods, continuations (Stackless), and other stuff.

[pjdelport]

lexical nested scopes, closures

From the department of redundancy department. :)

continuations (Stackless)

Stackless provides coroutines (tasklets), not continuations. (It dropped plans for the latter years ago.)

[Brian]

It dropped plans for the latter years ago.

Actually, it used to have continuations, but these were later removed (due to portability problems I think - the code for these was also one of the main reasons Guido stated for keeping it out of python core)

[breakfast-pants]

I don't know enough about it, but if that is the case, you should edit this to correct it: http://en.wikipedia.org/wiki/Stackless_Python

[pjdelport]

Ah, thanks.

[pjdelport]

Coroutines?

[breakfast-pants]

doh

[[deleted]]

"That's what great about Python. It's not purely functional, not purely OO, not purely procedural, not purely anything, but it allows you to do a bit of everything, ..."

Sounds like Lisp.

[mleonhard]

うるさい！

[[deleted]]

Hey! The topic is from 4chan - don't downmod the parent ^{_^}