Function _subsum

maths/bailey_borwein_plouffe.py:58–83

Private helper function to implement the summation functionality. @param digit_pos_to_extract: digit position to extract @param denominator_addend: added to denominator of fractions in the formula @param precision: same as precision in main function @return: floating-point n

(
    digit_pos_to_extract: int, denominator_addend: int, precision: int
)

def _subsum(
    digit_pos_to_extract: int, denominator_addend: int, precision: int
) -> float:
    # only care about first digit of fractional part; don't need decimal
    """
    Private helper function to implement the summation
    functionality.
    @param digit_pos_to_extract: digit position to extract
    @param denominator_addend: added to denominator of fractions in the formula
    @param precision: same as precision in main function
    @return: floating-point number whose integer part is not important
    """
    total = 0.0
    for sum_index in range(digit_pos_to_extract + precision):
        denominator = 8 * sum_index + denominator_addend
        if sum_index < digit_pos_to_extract:
            # if the exponential term is an integer and we mod it by the denominator
            # before dividing, only the integer part of the sum will change;
            # the fractional part will not
            exponential_term = pow(
                16, digit_pos_to_extract - 1 - sum_index, denominator
            )
        else:
            exponential_term = pow(16, digit_pos_to_extract - 1 - sum_index)
        total += exponential_term / denominator
    return total


if __name__ == "__main__":