Arithmetic Coding Interval Update

Problem

Update an arithmetic coding interval when the next symbol owns the cumulative range [cum_low, cum_high) inside the current interval. Return [low + width * cum_low, low + width * cum_high] where width = high - low.

Hint

Scale the cumulative range by the current interval width.

Test cases

case 1

in: [0,1,0,0.5]

expected: [0,0.5]

case 2

in: [0,1,0.5,1]

expected: [0.5,1]

case 3

in: [0.25,0.75,0.5,0.75]

expected: [0.5,0.625]

case 4

in: [0.1,0.3,0.2,0.9]

expected: [0.14,0.28]

Starter codePython

def arithmetic_update(low, high, cum_low, cum_high):
    # Your code here
    pass

4 test cases · run your code against them in the editor