Languages

• Formally, a language is a set of flat strings (sentences)
• In practice, each string in a language has a structure which can be described by a tree.
• Structure rules for sentences are defined by a grammar
• Example:
  • The sentences of a programming language are (legal) programs.
  • Programs are sentences of tokens (words). The structure of a program is given by a context-free grammar.
  • Words themselves are sequences of characters, the structure of words can also be given by a grammar.