Scheme 要求/键入racket中的合同失败

我试着查看文档，但找不到可用于我的案例的示例。我需要从srfi/1导入

这是我的尝试。这个例子在#lang racket中起作用

#lang typed/racket

(require/typed (only-in srfi/1 break)
               ;[break (All (T) (-> (-> T Boolean) (Listof T) (Listof T)))])
               ;[break (All (T) (-> (-> T Boolean) (Values (Listof T) (Listof T))))])
               [break (All (T) (-> (-> String (U False (Listof T))) (Listof T) (Listof T)))])

(define entity-types '("3DFACE"  "3DSOLID"  "ACAD_PROXY_ENTITY" "ARC" "ARCALIGNEDTEXT"  "ATTDEF"  "ATTRIB"  "BODY"  "CIRCLE" "DIMENSION" "ELLIPSE"  "HATCH" "IMAGE"  "INSERT"  "LEADER"  "LINE" "LWPOLYLINE" "MLINE"  "MTEXT"  "OLEFRAME"  "OLE2FRAME"  "POINT" "POLYLINE" "RAY"  "REGION"  "RTEXT"  "SEQEND"  "SHAPE"  "SOLID" "SPLINE" "TEXT"  "TOLERANCE"  "TRACE"  "VERTEX"  "VIEWPORT" "WIPEOUT" "XLINE"))
(define lst '("ENTITIES" "0" "LINE" "5" "BA1C" "330" "1F" "100" "AcDbEntity" "8" "0" "370" "0" "100" "AcDbLine" "10" "253.2926653556182" "20" "1478.621431186484" "30" "0.0" "11" "253.2876653556182" "21" "1478.621431186484" "31" "0.0" "0" "LINE" "5" "BA1D" "330" "1F" "100" "AcDbEntity" "8" "0" "370" "0" "100" "AcDbLine" "10" "253.2876653556182" "20" "1478.621431186484" "30" "0.0" "11" "253.2876653556182" "21" "1476.655431186484" "31" "0.0" "0" "LINE" "5" "BA1E" "330" "1F" "100" "AcDbEntity" "8" "0" "370" "0" "100" "AcDbLine" "10" "253.2926653556182" "20" "1476.655431186484" "30" "0.0" "11" "253.2876653556182" "21" "1476.655431186484" "31" "0.0" "0" "LINE" "5" "BA1F" "330" "1F" "100" "AcDbEntity" "8" "0" "370" "0" "100" "AcDbLine" "10" "253.2926653556182" "20" "1476.655431186484" "30" "0.0" "11"))

(break (lambda ([x : String]) (member x entity-types)) lst)

这对我很有用：

(require/typed (only-in srfi/1 break)
               [break (All (T) (-> (-> T (U False (Listof T))) (Listof T) 
                                   (values (Listof T) (Listof T))))])

请注意，

member

返回

#f

或其第一个元素为所搜索元素的列表。因此，示例

（lambda（[x:String]）（成员x实体类型））

中的谓词具有类型

（>T（U False（Listof T）））

---

最后，

值

需要指示

中断

返回多个值。

这是我将分配给

中断

的类型：

(require/typed
 (only-in srfi/1 break)
 [break (All [T] (-> (T -> Any) (Listof T) 
                     (Values (Listof T) (Listof T))))])

谓词函数可以返回任何内容。如果它返回

#f

，它将被视为falsy，而任何其他结果将被视为truthy。此外，正如soegaard提到的，

Values

类型构造函数需要指示

break

返回多个值

然而，Racket实际上包含一个非常类似于

break

的功能，但它实际上相当于

span

。函数本身被调用，并且根据该函数很容易实现

break

，而不是使用

srfi/1

(: break (All [T] (-> (T -> Any) (Listof T) 
                      (Values (Listof T) (Listof T)))))
(define (break pred lst)
  (splitf-at lst (negate pred)))