public MultipleFormalParameterSequence(FormalParameter formal, FormalParameterSequence formals,
                                        SourcePosition position)
     : base(position)
 {
     _formal  = formal;
     _formals = formals;
 }
 public ProcFormalParameter(Identifier identifier, FormalParameterSequence formals,
                            SourcePosition position)
     : base(position)
 {
     _identifier = identifier;
     _formals    = formals;
 }
 public FuncFormalParameter(Identifier identifier, FormalParameterSequence formals,
                            TypeDenoter type, SourcePosition position)
     : base(position)
 {
     _identifier = identifier;
     _formals    = formals;
     _type       = type;
 }