Gymnasium/gym/envs/algorithmic/reversed_addition.py

from __future__ import division
import numpy as np
from gym.envs.algorithmic import algorithmic_env

class ReversedAdditionEnv(algorithmic_env.GridAlgorithmicEnv):
    def __init__(self, rows=2, base=3):
        super(ReversedAdditionEnv, self).__init__(rows=rows, base=base, chars=False)

    def target_from_input_data(self, input_strings):
        curry = 0
        target = []
        for digits in input_strings:
            total = sum(digits) + curry
            target.append(total % self.base)
            curry = total // self.base

        if curry > 0:
            target.append(curry)
        return target

    @property
    def time_limit(self):
        # Quirk preserved for the sake of consistency: add the length of the input
        # rather than the length of the desired output (which may differ if there's
        # an extra carried digit).
        # TODO: It seems like this time limit is so strict as to make Addition3-v0
        # unsolvable, since agents aren't even given enough time steps to look at
        # all the digits. (The solutions on the scoreboard seem to only work by
        # save-scumming.)
        return self.input_width*2 + 4