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Topic 9 Symbol Manipulation Generating English Sentences

Topic 9 Symbol Manipulation Generating English Sentences. Section 2.3.2 This is an additional example to symbolic differentiation in book. October 2008. Example of Symbol Manipulation. One of the corner stones of Lisp/Scheme is its ability to easily manipulate symbols.

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Topic 9 Symbol Manipulation Generating English Sentences

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  1. Topic 9 Symbol ManipulationGenerating English Sentences Section 2.3.2 This is an additional example to symbolic differentiation in book. October 2008 Programming Development Techniques

  2. Example of Symbol Manipulation • One of the corner stones of Lisp/Scheme is its ability to easily manipulate symbols. • Because of this it has been heavily used in Artificial Intelligence. • As an example, we will write a program to manipulate English Sentences. Programming Development Techniques

  3. What makes an English Sentence? Consider very simple sentences (Context Free Grammar): S  NP VP NP  N | Adjective NP N  dog | cat | professor | student | rat Adjective  red | slow | dead VP  V | V Adverb V  ran | ate | slept | drank Adverb  quickly | happily | well Programming Development Techniques

  4. How might we generate using a Context Free Grammar? • Start with S • Find a rule whose left hand side matches S • Replace S with the right hand side of the rule • Continue Programming Development Techniques

  5. S  NP VP NP  N | Adjective NP N  dog | cat | professor | student | rat Adjective  red | slow | funny VP  V | V Adverb V  ran | ate | slept | studied Adverb  quickly | happily | well S NP VP N VP Professor VP V Professor ate Example Generation Programming Development Techniques

  6. S  the NP VP NP  N | Adjective NP N  dog | cat | professor | student | rat Adjective  red | slow | funny VP  V | V Adverb V  ran | ate | slept | studied Adverb  quickly | happily | well S The NP VP The Adjective NP VP The slow NP VP The slow Adjective NP VP The slow red NP VP The slow red N VP The slow red student VP The slow red student V Adverb The slow red student slept Adverb The slow red student slept happily Slight Modification Programming Development Techniques

  7. Implementation • Phrases will be represented as lists of words • Example: (ate) and (ate quickly) are both verb phrases. • Example: (professor) and (slow red professor) are both noun phrases. Programming Development Techniques

  8. Sentence Procedure • Creates a list of words that are “in the language” of the context free grammar defined earlier. • How? • Append them all together • SHOW CODE Programming Development Techniques

  9. Implications • Means that (noun-phrase) and (verb-phrase) are procedures that return lists of words • We saw in sentence, that it pretty much followed the right hand side of the rule Problem: • We have two right hand sides for each of noun-phrase and verb phrase • We want to randomly pick between them Programming Development Techniques

  10. Scheme allows random selection • (random 3) • Will select randomly between 0 1 2…. Programming Development Techniques

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