Ranya wrote: > Let's say I vreated my own CFG in python, How can I check now if a > sentence match this grammar (return true) or it doesn't match it (return > false and the wrong element in the grammar), How can I do this ?
Remember, context free grammars may be fine, but context free questions aren't ;) Is this question nltk-related? If so, here's one way (using a grammar found at http://www.nltk.org/book/ch08.html): >>> import nltk >>> grammar = nltk.CFG.fromstring(""" ... S -> NP VP ... VP -> V NP | V NP PP ... PP -> P NP ... V -> "saw" | "ate" | "walked" ... NP -> "John" | "Mary" | "Bob" | Det N | Det N PP ... Det -> "a" | "an" | "the" | "my" ... N -> "man" | "dog" | "cat" | "telescope" | "park" ... P -> "in" | "on" | "by" | "with" ... """) >>> parser = nltk.RecursiveDescentParser(grammar) >>> def check(sentence, parser=parser): ... return parser.parse_one(sentence) is not None ... >>> check("Mary saw the telescope".split()) True >>> check("Mary saw the saw".split()) False >>> check("Mary saw the chicken".split()) Traceback (most recent call last): [...] ValueError: Grammar does not cover some of the input words: "'chicken'". -- https://mail.python.org/mailman/listinfo/python-list
