# Last edited on 2004-11-06 20:37:44 by stolfi

The input to the grammar preprocessor consists of four parts:

  PREDICATES
    zero or more {PREDDEF}s

Predicate definitions:

  PREDDEF => PRED "(" MARKVAR ,.. ")" "=" "{" { "\n" MARKTUPLE }.. "\n" "}"
  
  MARKTUPLE => "(" MARKVAL ,.. ")"
  
    The marker values in the tuples must agree with the types of 
    the marker variables in the predicate's argument list.
  

  RULE => NTSYMBOL "{" RTAG "}" {"(" MARKER,.. ")"}? "->" FACTOR .. {COND}?

  PRED => [a-z][a-z0-9_]+

  COND => "!" PRED "(" MARKVAR,.. ")"
  
    In a {RULE} with a {COND}, the only valid {MARKVAR} assignments
    are those which, when substituted into the {COND}, yield one
    of the {PREDDEF}s listed in the preamble.