chriwong / plc_parser

SUBC Parser

A lexical analyzer, and a recursive descent parser for a (sort of) subset of C language called SUBC

Tricky Tokens

• Quotes
  • Must be single quote, followed by anything but a single quote, followed by a single quote
  • regex '.'
• Strings
  • Must be double quotes, followed by any number of characters other than double quotes, followed by double quotes
  • regex "[^"]*"
• Colon
  • Can be just colon, colon-equals, or colon-equals-colon
  • : := :=:
• Inequality Signs
  • For a token beginning with less-than, can be less-than, less-than-equals, or less-than-greater-than
  • < <= <>
  • For a token beginning with greater-than, can be greater-than or greater-than-equals

  • =

• Dot
  • Can be dot or dot-dot
  • . ..
• Other symbols
  • Plus, minus, star, forward-slash, semicolon, comma, open/close parentheses, and open/close braces are all valid
  • • • • / ; , ( )
• Comments
  • Braces and all text between them should be ignored. An octothorpes and all text on the same line following it should also be ignored
  • {.*}

• Identifiers
  • A valid identifier begins with a letter underscore and is followed by any number of letters, numbers, or underscores
  • regex ([A-Z]|[a-z]|)([a-z]|[A-Z]|[0-9]|)*