mathdatech/Python
1
0
Fork 0
mirror of https://github.com/TheAlgorithms/Python.git synced 2025-02-14 13:28:09 +00:00
Code Issues Packages Projects Releases Wiki Activity

Cleanup comments

Browse Source 
Few typos, debugging advice
This commit is contained in:
Bill Breitmayer 2024-05-31 09:04:55 -04:00
parent 82695f895e
commit 6e81a51620
1 changed files with 12 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
bit_manipulation/multibit_manipulation.py
View File

@ -31,7 +31,7 @@ The bitwise expressions may look convoluted, but basically, there are
just three parts: left-hand side, value, right-hand side.
For example, say you want to insert two ones in the middle of 0b101101,
that is -> 0b10111101. Index is 2 ( 0 ,1, 2 from the right ) and the
that is -> 0b10111101. Index is 3 ( 0 ,1, 2, 3 from the right ) and the
value is 3 (0b11) with a bit length of 2.
- Shift >> index right to produce 0b101
@ -44,15 +44,21 @@ value is 3 (0b11) with a bit length of 2.
-> 0b10111101.
To remove the center two bits of 0b101101 -> 0b1001, the process is mostly
the same.
the same. Index is 2 for the remove operation on the right-center bit
rather than 3 for inserting, because we are referring to the bit itself
rather the position to the right of the bit index.
- The initial right shift is index(2) + bit_length(2), taking out the two
- The initial right shift is index (2 ) + bit_length(2), taking out the two
middle bits and producing 0b10.
- The left shift of index produces 0b1000.
- The original bint is ANDed with bitmask 0b11 producing 0b01 which is
ORed with 0b1000 yielding the target 0b1001.
It's not so bad once you get the hang of it.
It's not so bad once you get the hang of it, although it can still be a
bear to debug. In the insert example above, the result of inserting 0b11
in the center ( index=3 ) or to the right ( index=2 ) produces the same
correct result despite the misspecification. These algorithms are very
fast but can be touchy at times.
Various bit insert/remove solutions exist using bin() string functions
and slicing, but this bitwise implementation is significantly faster
@ -64,10 +70,6 @@ See https://github.com/billbreit/BitWiseApps/blob/main/dev/time_ops.py
bit_length = int.bit_length
"""The only consistent error checking is for bint < 0 or index < 0 etc.,
and for bit_length(value) > bit_len, which can cause silent errors.
Anything like int(None) is going to cause a loud error. """
def bit_get(bint: int, index: int) -> int:
"""Get value of bit at index in bint.
@ -197,7 +199,7 @@ def multibit_set(bint: int, index: int, bit_len: int, value: int) -> int:
def multibit_insert(bint: int, index: int, bit_len: int, value: int) -> int:
"""Insert before index-th slot
"""Insert value before index-th slot
>>> multibit_insert(0, 1, 1, 1)
2
@ -245,6 +247,7 @@ def multibit_remove(bint: int, index: int, bit_len: int) -> int:
if __name__ == "__main__":
import doctest
doctest.testmod()