B P?[ @sbddlmZddlZddlZddlmZdddZddZdd Zd Z dd d Z e dkr^e dS))print_functionN) NonterminalcCs<|s |}|dkrtj}t||g|}|r8t||}|S)am Generates an iterator of all sentences from a CFG. :param grammar: The Grammar used to generate sentences. :param start: The Nonterminal from which to start generate sentences. :param depth: The maximal depth of the generated tree. :param n: The maximum number of sentences to return. :return: An iterator of lists of terminal tokens. N)startsysmaxsize _generate_all itertoolsislice)grammarrdepthniterr2lib/python3.7/site-packages/nltk/parse/generate.pygenerates  rc cs|ryFx@t||d|D],}x&t||dd|D]}||Vq2WqWWqtk r}z|jdkrptdnWdd}~XYqXngVdS)Nrz maximum recursion depth exceededz7The grammar has rule(s) that yield infinite recursion!!) _generate_oner RuntimeErrormessage)r itemsr Zfrag1Zfrag2Z_errorrrrr(s rccsZ|dkrVt|trNxB|j|dD](}x"t|||dD] }|Vq:Wq Wn|gVdS)Nr)Zlhsr) isinstancerZ productionsrZrhs)r itemr ZprodZfragrrrr:s  rz S -> NP VP NP -> Det N PP -> P NP VP -> 'slept' | 'saw' NP | 'walked' PP Det -> 'the' | 'a' N -> 'man' | 'park' | 'dog' P -> 'in' | 'with' cCsfddlm}td|ftt|t}x4tt||ddD]\}}td|d|fq@WdS)Nr)CFGz3Generating the first %d sentences for demo grammar:)r rz%3d. %s ) nltk.grammarrprint demo_grammarZ fromstring enumeraterjoin)Nrr r ZsentrrrdemoOs   r!__main__)NNN)r) Z __future__rrrrrrrrrr!__name__rrrr s