require/typed 球拍合约失败

Question

我试过查看文档，但找不到可用于我的案例的示例。我需要从 srfi/1 导入 break。

这是我的尝试。该示例适用于#lang 球拍。

#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)

Answer 1

这对我有用：

(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 returns #f 或第一个元素是要搜索的元素的列表。因此示例 (lambda ([x : String]) (member x entity-types)) 中的谓词具有类型 (-> T (U False (Listof T))).

最后需要values表示breakreturns多个值

Answer 2

这是我要分配给 break 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return任何东西。如果它 returns #f，它将被视为 falsy，而任何其他结果都将被视为 truthy。此外，正如 soegaard 提到的，需要 Values 类型构造函数来指示 break return 的多个值。

然而，Racket实际上包含了一个与break非常相似的功能，但它实际上等同于span。该函数本身称为 splitf-at，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)))

require/typed 球拍合约失败

require/typed contract in racket fails

scheme

racket

typed-racket