我已经为一种非常简单的语言编写了一个使用 megaparsec 的解析器,该语言由整数文字和两个一元运算符“a”和“b”组成:
data ValueExpr = OpA ValueExpr
| OpB ValueExpr
| Integer Integer
valueExpr :: Parser ValueExpr
valueExpr = makeExprParser valueTerm valueOperatorTable
valueTerm :: Parser ValueExpr
valueTerm = parenthesised valueExpr
<|> Integer <$> integerLiteral
integerLiteral :: Parser Integer
integerLiteral = -- omitted
valueOperatorTable :: [[Operator Parser ValueExpr]]
valueOperatorTable = [[unaryOp "a" AOp,
unaryOp "b" BOp]]
parenthesised :: Parser a -> Parser a
parenthesised = between (char '(') (char ')')
unaryOp :: Text -> (a -> a) -> Operator Parser a
unaryOp name f = Prefix (f <$ symbol name)
binaryOp :: Text -> (a -> a -> a) -> Operator Parser a
binaryOp name f = InfixL (f <$ symbol name)
但是,这似乎不允许我“链接”一元运算符,即在尝试解析“ab1”时,我遇到了“意外的'b'”。这是为什么?