compTheory - Theory of Computation-Formal language theory...

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Theory of Computation -Formal language theory -- “How are languages defined?” -The investigation of computability – “What is algorithm?”, “What are the capabilities and limitations of algorithmic computation?” (When we are given a problem to solve by writing a program, how can we be sure if there is an algorithm to solve the problem? It might be impossible to write such a program. There are limitations of algorithmic computation. ) The computations of a machine can be used to recognize a language. An input string is accepted by the machine if the computation initiated with the string indicates its syntactic correctness. Each machine has an associated language, the set of strings accepted by the machine. The computational capabilities of each family of abstract machines is characterized by the languages accepted by the machine in the family. Language Theory -Most programs take some input and produce output. -Some inputs are valid and some are not. -For invalid inputs, the program should not just hang. It should be more robust and user-friendly. -In other words, programs (or program modules) must recognize what inputs are valid and what are not. -The set of valid inputs are referred as input language. (A language, in general, is a set of strings made of some alphabet). -In general we often need modules that recognize languages. -There is a hierarchy of languages. Regular expressions -> Context Free Languages -> Context Sensitive Languages -> Decidable -> Undecidable Compiler input programs accepted or rejected
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Context-Free Grammars are used to generate the strings of a language by enforcing the syntactic restrictions of the language.
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This note was uploaded on 11/09/2010 for the course CSE 71682 taught by Professor Nakamura during the Spring '10 term at ASU.

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compTheory - Theory of Computation-Formal language theory...

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