使用替代模型的评估函数中的DrRacket类型不匹配错误
我已经实现了语言“ROL”,现在我正在尝试扩展该语言以支持fun和call,我正在尝试在替换模型中实现它 下面是我的eval函数代码(注意,这段代码在没有乐趣和调用的情况下运行得很好。所以问题一定是这两个实现的问题使用替代模型的评估函数中的DrRacket类型不匹配错误,racket,eval,call,substitution,Racket,Eval,Call,Substitution,我已经实现了语言“ROL”,现在我正在尝试扩展该语言以支持fun和call,我正在尝试在替换模型中实现它 下面是我的eval函数代码(注意,这段代码在没有乐趣和调用的情况下运行得很好。所以问题一定是这两个实现的问题 (: eval : RegE -> RES) ;; evaluates RegE expressions by reducing them to bit-lists (define (eval expr) (cases expr [(Reg right) (RegV
(: eval : RegE -> RES)
;; evaluates RegE expressions by reducing them to bit-lists
(define (eval expr)
(cases expr
[(Reg right) (RegV right)]
[(Bool b) (RES_Bool b)]
[(Id name) (error 'eval "free identifier: ~s" name)]
[(And left right) (reg-arith-op bit-and (eval left ) (eval right) )]
[(Or left right) (reg-arith-op bit-or (eval left ) (eval right) )]
[(Shl E1) (RegV (shift-left (RegV->bit-list (eval E1))))]
[(Maj E1) (RES_Bool (majority? (RegV->bit-list (eval E1))))]
[(Geq E1 E2) (RES_Bool (geq-bitlists? (RegV->bit-list (eval E1)) (RegV->bit-list (eval E2))))]
[(With bound-id named-expr bound-body)
(eval (subst bound-body
bound-id
(Reg (RegV->bit-list(eval named-expr)))))]
[(Fun bound-id bound-body) expr]
[(Call fun-expr arg-expr)
(let ([fval (eval fun-expr)])
(cases fval
[(Fun bound-id bound-body)
(eval (subst bound-body
bound-id
(eval arg-expr)))]
[else (error 'eval "`call' expects a function, got: ~s"
fval)]))]
[(If E1 E2 E3) (if (RegV->boolean (eval E1)) (eval E2) (eval E3))]
))
这是我的sunst函数:
(define (subst expr from to)
(cases expr
[(Reg g) expr]
[(Bool g) expr]
[(And left right)(And (subst left from to)(subst right from to))]
[(Or left right)(Or (subst left from to)(subst right from to))]
[(If bool ifBody elseBody) (If (subst bool from to) (subst ifBody from to) (subst elseBody from to))]
[(Maj left)(Maj (subst left from to))]
[(Geq left right)(Geq (subst left from to)(subst right from to))]
[(Shl left)(Shl (subst left from to))]
[(Id name) (if (eq? name from) to expr)]
[(With bound-id named-expr bound-body)
(if (eq? bound-id from)
expr
(With bound-id
named-expr
(subst bound-body from to)))]
[(Call left right) (Call (subst left from to) (subst right from to))]
[(Fun bound-id bound-body)
(if (eq? bound-id from)
expr
(Fun bound-id (subst bound-body from to)))]))
我得到了错误信息:
Type Checker: type mismatch
expected: RegE
given: RES in: fval
. Type Checker: type mismatch
expected: RegE
given: RES in: (eval arg-expr)
. Type Checker: type mismatch
expected: RES
given: Fun in: (cases expr ((Reg right) (RegV right)) ((Bool b) (RES_Bool b)) ((Id name) (error (quote eval) "free identifier: ~s" name)) ((And left right) (reg-arith-op bit-and (eval left) (eval right))) ((Or left right) (reg-arith-op bit-or (eval left) (eval right))) ((Shl E1) (RegV (shift-left (RegV->bit-list (eval E1))))) ((Maj E1) (RES_Bool (majority? (RegV->bit-list (eval E1))))) ((Geq E1 E2) (RES_Bool (geq-bitlists? (RegV->bit-list (eval E1)) (RegV->bit-list (eval E2))))) ((With bound-id named-expr bound-body) (eval (subst bound-body bound-id (Reg (RegV->bit-list (eval named-expr)))))) ((Fun bound-id bound-body) expr) ((Call fun-expr arg-expr) (let ((fval (eval fun-expr))) (cases fval ((Fun bound-id bound-body) (eval (subst bound-body bound-id (eval arg-expr)))) (else (error (quote eval) "`call' expects a function, got: ~s" fval))))) ((If E1 E2 E3) (if (RegV->boolean (eval E1)) (eval E2) (eval E3))))
. Type Checker: Summary: 3 errors encountered in:
fval
(eval arg-expr)
(cases expr ((Reg right) (RegV right)) ((Bool b) (RES_Bool b)) ((Id name) (error (quote eval) "free identifier: ~s" name)) ((And left right) (reg-arith-op bit-and (eval left) (eval right))) ((Or left right) (reg-arith-op bit-or (eval left) (eval right))) ((Shl E1) (RegV (shift-left (RegV->bit-list (eval E1))))) ((Maj E1) (RES_Bool (majority? (RegV->bit-list (eval E1))))) ((Geq E1 E2) (RES_Bool (geq-bitlists? (RegV->bit-list (eval E1)) (RegV->bit-list (eval E2))))) ((With bound-id named-expr bound-body) (eval (subst bound-body bound-id (Reg (RegV->bit-list (eval named-expr)))))) ((Fun bound-id bound-body) expr) ((Call fun-expr arg-expr) (let ((fval (eval fun-expr))) (cases fval ((Fun bound-id bound-body) (eval (subst bound-body bound-id (eval arg-expr)))) (else (error (quote eval) "`call' expects a function, got: ~s" fval))))) ((If E1 E2 E3) (if (RegV->boolean (eval E1)) (eval E2) (eval E3))))
>
我的数据类型是:
(define-type RegE
[Reg Bit-List]
[Xor RegE RegE]
[And RegE RegE]
[Or RegE RegE]
[Shl RegE]
[Id Symbol]
[With Symbol RegE RegE]
[Bool Boolean]
[Geq RegE RegE]
[Maj RegE]
[If RegE RegE RegE]
[Fun Symbol RegE]
[Call RegE RegE])
以及:
我可以看到,对于
(let([fval(eval-fun-expr)
执行(eval-fun-expr)
将返回RES,我猜这可能是问题所在,是否有其他方法可以解决它?请提供任何帮助。关键问题是您希望如何在运行时表示函数。
eval
的定义是:
(: eval : RegE -> RES)
;; evaluates RegE expressions by reducing them to bit-lists
(define (eval expr)
(cases expr
...
[(Fun bound-id bound-body) expr]
...
计算(趣味绑定id绑定body)
的结果需要是一个RES。
可将RES扩展为:
(define-type RES
[RES_Bool Boolean]
[RegV Bit-List]
[FunV Symbol RegE])
然后让eval
返回一个(FunV绑定id绑定体)
在呼叫评估中,您需要切换到
(cases fval
[(FunV bound-id bound-body)
因为
fval
是一个RES.只是为了确保:您使用的是eopl?不,我使用的是plOk,Barzilays语言。您可以发布您的数据类型吗?是的,我刚刚尝试了这个,它确实修复了第一个错误,但第二个和第三个错误保持不变。对不起,我的错了,它给了我类型检查器:类型不匹配预期:RegE给定:RES in:(eval arg expr)当您计算(eval arg expr)
时,我将fun更改为[(fun-bound-id-body)(FunV-bound-id-body)]后出错。但是subst
需要一个RegE。因此将(eval-arg expr)
更改为arg expr
。
(cases fval
[(FunV bound-id bound-body)