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fixed fixed point algorithms in python

This commit is contained in:
Peter McGoron 2022-10-27 17:55:12 -04:00
parent 4f85146d61
commit 440f144180
1 changed files with 7 additions and 7 deletions
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12
doc/fixedpoint.py
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@ -1,5 +1,6 @@
# Functions for converting to and from fixed point in Python. # Functions for converting to and from fixed point in Python.
from math import log10, floor from math import log10, floor
from decimal import *
def string_to_fixed_point(s, fracnum): def string_to_fixed_point(s, fracnum):
l = s.split('.') l = s.split('.')
@ -11,10 +12,8 @@ def string_to_fixed_point(s, fracnum):
dec = 10 dec = 10
frac = 0 frac = 0
frac_decimal = int(l[1]) frac_decimal = Decimal(f'0.{l[1]}')
# get the smallest power of ten higher then frac_decimal # get the smallest power of ten higher then frac_decimal
frac_decimal_len = floor(log10(frac_decimal) + 1)
pow10 = 10**frac_decimal_len
frac = 0 frac = 0
# Example: # Example:
@ -24,13 +23,14 @@ def string_to_fixed_point(s, fracnum):
# 0.9134 = a.bcdefgh ... # 0.9134 = a.bcdefgh ...
# therefore a = 0. Then remove the most significant digit. # therefore a = 0. Then remove the most significant digit.
# Then multiply by 2 again. Then # Then multiply by 2 again. Then
# 18268 = b.cdefgh ... # 1.8268 = b.cdefgh ...
# therefore b = 1. Then take 8268, and so on. # therefore b = 1. Then take 8268, and so on.
for i in range(0,fracnum): for i in range(0,fracnum):
frac_decimal = frac_decimal * 2 frac_decimal = frac_decimal * 2
div, mod = divmod(frac_decimal, pow10) div = floor(frac_decimal)
frac = div | (frac << 1) frac = div | (frac << 1)
frac_decimal = mod frac_decimal = frac_decimal - div
whole = int(l[0]) whole = int(l[0])
if whole < 0: if whole < 0: