util.py 450 B

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  1. # Natural Language Toolkit
  2. #
  3. # Copyright (C) 2001-2020 NLTK Project
  4. # Author: Ilia Kurenkov <ilia.kurenkov@gmail.com>
  5. # URL: <http://nltk.org/>
  6. # For license information, see LICENSE.TXT
  7. """Language Model Utilities"""
  8. from math import log
  9. NEG_INF = float("-inf")
  10. POS_INF = float("inf")
  11. def log_base2(score):
  12. """Convenience function for computing logarithms with base 2."""
  13. if score == 0.0:
  14. return NEG_INF
  15. return log(score, 2)