integers: add support for bit_length() and bit_set()

On Python, from version 2.8, int has the method bit_length

While developing on different versions of Python, I use this:

def bit_length(x):
	if hasattr(x, "bit_length") :
		return	x.bit_length()
	i = 0
	while x :
		x = x >> 1
		i += 1
	return	i

assert	bit_length(0) == 0
assert	bit_length(1) == 1
assert	bit_length((1 << 64) - 1) == 64

Python doesn't have a built-in bit_set, but it is very useful:

def bit_set(x) :
	i = 0
	while x :
		x = x & (x - 1)
		i += 1
	return	i

assert	bit_set(0) == 0
assert	bit_set(1) == 1
assert	bit_set(1 << 64) == 1

The two algorithms are efficient, simple and straightforward to code in C.

Could you please implement them on the int type ?

I see bit_length() and bit_count() in the Python documentation, but not bit_set().

bit_set will certainly not be implemented since - as you've mentioned - it's non-standard.

bit_length could be implemented, however, it's very easy to work-around (with a python example even given in the documentation).

In general (and also applying to the other issues you've raised), MicroPython has to balance size of implementation with usefulness and convenience. If you really feel strongly that bit_length is necessary, I suggest raising a PR with an implementation (as you've said, it's quite simple) and we can see how large the implementation is and decide whether it's worthwhile.

@mattytrentini

Hi @mattytrentini

I know bit_set isn't standard.

They are two useful functions, working close to hardware.

IMHO the python example
https://docs.python.org/3/library/stdtypes.html#int.bit_length
is an exampe of terrible programming.

They are usable on Python running on desktop pc, useless on micro for bit-banging and the like.

Please, is there a How to on PR?
Even better, an example of coding a basic function?

Do I need special privileges to open a PR?

Thanks

Do I need special privileges to open a PR?

No.

Please, is there a How to on PR?

It's a github thing. See https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/creating-a-pull-request

Python doesn't have a built-in bit_set,

Your code example seems to perform the bit_count() operation.

we can see how large the implementation is

BTW, I think the implemetation will be tiny.
It isn't rocket science, just basic functions :-)

I'm willing to try to code the two functions, I've been developing in C (and other languages, on servers and on micros) for 30 years.
I need a little help getting started.

Iirc for bit_length there already exists an old pull request.

Iirc for bit_length there already exists an old pull request.

Sure? Do you know the PR number? A search does not reveal it.

It looks like it is attached to this issue, but no PR was made: #4065

I meant that.

It looks like it is attached to this issue, but no PR was made: #4065

Thanks David, I'll close this and continue the discussion on #4065.

Navigation Menu

Repository navigation

integers: add support for bit_length() and bit_set() #11618

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

integers: add support for bit_length() and bit_set() #11618

Description

Activity

robert-hh commented on May 25, 2023

mattytrentini commented on May 25, 2023

massimosala commented on May 25, 2023

robert-hh commented on May 25, 2023

robert-hh commented on May 25, 2023

massimosala commented on May 25, 2023

rkompass commented on May 25, 2023

robert-hh commented on May 25, 2023

dlech commented on May 25, 2023

rkompass commented on May 25, 2023

massimosala commented on May 30, 2023

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions