Parsing Haskell, problems

• The layout rules require interaction bewtween the lexer and the parser.
• The precedence and associativity of infix operators is not easily available.
  • Infix declarations can be put wherever a type signature is allowed, even after a use of the operator.
  • Fixity follows the scope of a specific binding, so you have to know which identifiers are in scope and where they were originally defined.
  • Determining the fixity of imported operators requires a full-fledged implementation of the module system!