import edu.neu.ccs.demeter.dj.* ;
import java.util.*;

CSP = List(ConstraintSatisfactionProblem) EOF.
ConstraintSatisfactionProblem =
"preamble" Preamble <constraints> List(Constraint).
Constraint : Satisfied | Unsatisfied | ProperConstraint common [Weight].
Preamble = 
  "numVariables" <numVariables> int 
  "numConstraints" <numConstraints> int 
  "relations" List(RelationName) 
"end".
// Meaning of relations is predefined
ProperConstraint = RelationName "(" <literals> List(Literal) ")".
Literal : Pos | Neg common Variable.
Pos = .
Neg = "!".
Satisfied = "sat".
Unsatisfied = "unsat".
Variable = <v> Ident.
RelationName = <v> Ident.
Weight = <v> int.
List(S) ~ {S}.
Main = .
// semantic checks: 
// cg.gather(csp, "from CSP to Variable") viewed as set . size() = numVariables

// length of constraints = numConstraints

// cg.gather(csp, "from CSP via Preamble to RelationName") viewed as set same set as
// cg.gather(csp, "from CSP via Constraint to RelationName") viewed as set