anchor.diff:     ;
   
   prefixExpr
  -   : UnaryOp? (blockExpr | simpleExpr1)
  +   : UnaryOp? (closureExpr | blockExpr | simpleExpr1)
      ;
   
   simpleExpr1:
  
positive.code: letins:
     'let' letbind (',' letbind)* 'in' expr;
  
  expr:
       ifExpr
     | letins
     | infixExpr
     ;
  
negative.code:    : expr (',' expr)*
     ;
  
  closureExpr:
     '{' params ARROW block '}'
     ;
  
  blockExpr:
  	'{' block '}'
     ;
  