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POTrying to generate all sentences of a simple formal grammar
 

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  1. POTrying to generate all sentences of a simple formal grammar
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    <p>I am new to python and trying to generate all sentences possible in the grammar. Here is the grammar:</p> <pre><code> #set of non terminals N = ('&lt;subject&gt;', '&lt;predicate&gt;', '&lt;noun phrase&gt;', '&lt;noun&gt;', '&lt;article&gt;', '&lt;verb&gt;', '&lt;direct object&gt;') #set of teminals T = ('the', 'boy', 'dog', 'bit') #productions P = [ ('Sigma', ['&lt;subject&gt;', '&lt;predicate&gt;']), \ ('&lt;subject&gt;', ['&lt;noun phrase&gt;']), \ ('&lt;predicate&gt;', ['&lt;verb&gt;']), \ ('&lt;predicate&gt;', ['&lt;verb&gt;','&lt;direct object&gt;']), \ ('&lt;noun phrase&gt;', ['&lt;article&gt;','&lt;noun&gt;']), \ ('&lt;direct object&gt;', ['&lt;noun phrase&gt;']), \ ('&lt;noun&gt;', ['boy']), \ ('&lt;noun&gt;', ['dog']), \ ('&lt;article&gt;', ['the']), \ ('&lt;verb&gt;', ['bit']) ] </code></pre> <p>Here is my attempt, I am using a queue class to implement it methodically,</p> <pre><code># language defined by the previous grammar. Q = Queue() Q.enqueue(['Sigma']) found = 0 while 0 &lt; len(Q): print "One while loop done" # Get the next sentential form sf = Q.dequeue() sf1 = [y for y in sf] for production in P: for i in range(len(sf1)): if production[0] == sf1[i]: sf[i:i+1] = [x for x in production[1]] Q.enqueue(sf) Q.printQ() </code></pre> <p>I am getting in infinite loop, and also I am facing some issue with shallow-deep copy, if I change one copy of sf, everything in queue changes too. Any help is appreciated, any directions, tips would be great</p> <p>Here is the expected output:</p> <pre><code> The dog bit the boy The boy bit the dog The boy bit the boy The dog bit the dog The dog bit The boy bit </code></pre>
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    1. USuser1772218
    1. USuser1772218
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      1. POTrying to generate all sentences of a simple formal grammar
      1. USSimon K Bhatta4ya
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    2. VO
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      1. POTrying to generate all sentences of a simple formal grammar
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      1. VTUpMod
    1. COYour indentation is broken. Recopy it from your source file, then select the code and press Ctrl-K to format it. If you don't get the indentation right, we can't tell how Python thinks your code is structured.
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      1. POTrying to generate all sentences of a simple formal grammar
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    2. COI have fixed the indentation. This is all I did, as I am getting in an infinite loop. Thanks for taking a look. Appreciate it
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      1. POTrying to generate all sentences of a simple formal grammar
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    3. COYou're asking us to write your algorithm for you.
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      1. POTrying to generate all sentences of a simple formal grammar
      1. USGames Brainiac
 

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