473,586 Members | 2,490 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

My tail call optimizing decorator

Please critique this tail call optimizing decorator I've written. I've
tried to fix the pitfalls of other proposed decorators, and the result
is this one that supports mutual recursion, does not use exceptions,
stack inspection or any implementation-dependent hack, and is pretty
short and fast - the fastest out of the ones I could find and try. In
fact, in tail-recursive environments I tested the impact of using the
decorator is difficult to even measure, as the extra time the
decorator takes to run is probably saved by the better use of cache
memory. The only caveat is that if used in a function that's not
called in a tail-recursive fashion, bad things will happen.

def tailcall(f):
'''Decorator that implements tail call optimization.

Supports cooperative tail call - even when only one of the functions
decorated, and all exceptions pass through it. You can tell the
that have been tail optimized because they have "tco" before them in
stack frame.

The only caveat is that if you attempt to decorate a function that
called in a tail recursive fashion from another decorated function,
get wrong results.'''
tdata = [False] #[Optimizing?]
DO_CALL = object() #Call marker
def tco(*a, **aa):
if tdata[0]:
return DO_CALL, a, aa
tdata[0] = True
ret = f(*a, **aa)
while type(ret) is tuple and ret and ret[0] is DO_CALL:
ret = f(*ret[1], **ret[2])
tdata[0] = False
return ret
tco.__doc__ = f.__doc__
return tco

Sep 26 '07 #1
0 1255

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

by: Christopher T King | last post by:
Is it feasable, and/or desirable to have Python optimize tail-recursive calls, similar to Scheme and gcc -O2? i.e. effectively compile this: def foo(n): return foo(n-1) into this: def foo(n): goto foo(n-1)
by: Stephen Thorne | last post by:
Decorators have been getting lots of air-time at the moment, but only really the syntax. After a short discussion on irc the other night I decided to download python2.4 from experimental and write out some truely worthy decorator hacks. I implemented multimethods as a warm-up, and then implemented tail call elimination. Presented here is a...
by: Crutcher | last post by:
This is fun :) {Note: I take no responsibilty for anyone who uses this in production code} #!/usr/bin/env python2.4 # This program shows off a python decorator # which implements tail call optimization. It # does this by throwing an exception if it is # it's own grandparent, and catching such # exceptions to recall the stack.
by: Ole Nielsby | last post by:
I just wonder if this is possible with C++/clr. I'm trying to .NET-enable an interpreter for a Lisp flavoured language, the interpreter written in NASM which I have managed to port to MASM. However the VS2005 debugger is giving me a really hard time - seems it doesn't cope well with mixing MASM with C++/clr, so I am considering a rewrite...
by: Kay Schluehr | last post by:
by: ssecorp | last post by:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/496691 so I try it and when I run: @Decorators.tail_recursion def fibtr(n): def fibt(a, b, n): if n <= 1: return b else: return fibt(b, a + b, n - 1)
by: mh | last post by:
I am instantiating a class A (which I am importing from somebody else, so I can't modify it) into my class X. Is there a way I can intercept or wrape calls to methods in A? I.e., in the code below can I call x.a.p1() and get the output
by: Muzammil | last post by:
int harmonic(int n) { if (n=1) { return 1; } else { return harmonic(n-1)+1/n; } } can any help me ??
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main...
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. ...
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that...
by: Hystou | last post by:
Overview: Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows Update option using the Control Panel or Settings app; it automatically checks for updates and installs any it finds, whether you like it or not. For...
by: tracyyun | last post by:
Dear forum friends, With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each protocol has its own unique characteristics and advantages, but as a user who is planning to build a smart home system, I am a bit confused by the...
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert...
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in...
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.