pipeline/nltk/test/bleu.doctest

==========
BLEU tests
==========

>>> from nltk.translate import bleu

If the candidate has no alignment to any of the references, the BLEU score is 0.

>>> bleu(
...     ['The candidate has no alignment to any of the references'.split()],
...     'John loves Mary'.split(),
...     (1,),
... )
0

This is an implementation of the smoothing techniques
for segment-level BLEU scores that was presented in
Boxing Chen and Collin Cherry (2014) A Systematic Comparison of
Smoothing Techniques for Sentence-Level BLEU. In WMT14.
http://acl2014.org/acl2014/W14-33/pdf/W14-3346.pdf
>>> from nltk.translate.bleu_score import sentence_bleu,SmoothingFunction


>>> sentence_bleu(
...     ['It is a place of quiet contemplation .'.split()],
...     'It is .'.split(),
...     smoothing_function=SmoothingFunction().method4,
... )*100
4.4267...