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Recognizers vs. Generators

• We don't want to use English to describe a language (too long, tedious, imprecise), so ...

• There are two formal approaches to describing syntax:
  • Recognizers
    • Given a string, a recognizer for a language L tells whether or not the string is in L (ex: Compiler)
  • Generators
    • A generator for L will produce an arbitrary string in L on demand. (ex: Grammar, BNF)
  • Recognition and generation are useful for different things, but are closely related