-- expressionPair ::= (Expression, Expression)
expressionPair :: Parser (Expression, Expression)
expressionPair = parens $ do
  expr1 <- expression
  comma
  expr2 <- expression
  return (expr1, expr2)

-- | ConstExpr ::= Number
expressionPair :: Parser (Expression, Expression)
expressionPair = parens $ do
  expr1 <- expression
  comma
  expr2 <- expression
  return (expr1, expr2)

-- | ConstExpr ::= Number
expressionPair = parens $ do
  expr1 <- expression
  comma
  expr2 <- expression
  return (expr1, expr2)

-- | ConstExpr ::= Number