{"id":8975,"date":"2024-10-21T13:26:17","date_gmt":"2024-10-21T12:26:17","guid":{"rendered":"https:\/\/solidt.eu\/site\/?p=8975"},"modified":"2024-10-21T13:26:19","modified_gmt":"2024-10-21T12:26:19","slug":"delphi-pascal-iteratorwrapper","status":"publish","type":"post","link":"https:\/\/solidt.eu\/site\/delphi-pascal-iteratorwrapper\/","title":{"rendered":"Delphi \/ Pascal IteratorWrapper"},"content":{"rendered":"\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">uses\n  System.SysUtils, System.Generics.Collections;\n\ntype\n  TIteratorWrapper&lt;T> = class\n  private\n    FEnumerable: TEnumerable&lt;T>;\n  public\n    constructor Create(Iterable: TEnumerable&lt;T>);\n    function Map(Func: TFunc&lt;T, T>): TIteratorWrapper&lt;T>;\n    function Filter(Func: TFunc&lt;T, Boolean>): TIteratorWrapper&lt;T>;\n    function Take(N: Integer): TIteratorWrapper&lt;T>;\n    function ToArray: TArray&lt;T>;\n    function GetEnumerator: TEnumerator&lt;T>;\n  end;\n\nconstructor TIteratorWrapper&lt;T>.Create(Iterable: TEnumerable&lt;T>);\nbegin\n  FEnumerable := Iterable;\nend;\n\nfunction TIteratorWrapper&lt;T>.Map(Func: TFunc&lt;T, T>): TIteratorWrapper&lt;T>;\nvar\n  Enumerator: TEnumerator&lt;T>;\nbegin\n  Result := TIteratorWrapper&lt;T>.Create(\n    TEnumerable&lt;T>.Create(\n      function: TEnumerator&lt;T>\n      begin\n        Enumerator := FEnumerable.GetEnumerator;\n        Result := TEnumerator&lt;T>.Create(\n          function: Boolean\n          begin\n            Result := Enumerator.MoveNext;\n            if Result then\n              Enumerator.Current := Func(Enumerator.Current);\n          end\n        );\n      end\n    )\n  );\nend;\n\nfunction TIteratorWrapper&lt;T>.Filter(Func: TFunc&lt;T, Boolean>): TIteratorWrapper&lt;T>;\nvar\n  Enumerator: TEnumerator&lt;T>;\nbegin\n  Result := TIteratorWrapper&lt;T>.Create(\n    TEnumerable&lt;T>.Create(\n      function: TEnumerator&lt;T>\n      begin\n        Enumerator := FEnumerable.GetEnumerator;\n        Result := TEnumerator&lt;T>.Create(\n          function: Boolean\n          begin\n            while Enumerator.MoveNext do\n            begin\n              if Func(Enumerator.Current) then\n                Exit(True);\n            end;\n            Result := False;\n          end\n        );\n      end\n    )\n  );\nend;\n\nfunction TIteratorWrapper&lt;T>.Take(N: Integer): TIteratorWrapper&lt;T>;\nvar\n  Count: Integer;\n  Enumerator: TEnumerator&lt;T>;\nbegin\n  Count := 0;\n  Result := TIteratorWrapper&lt;T>.Create(\n    TEnumerable&lt;T>.Create(\n      function: TEnumerator&lt;T>\n      begin\n        Enumerator := FEnumerable.GetEnumerator;\n        Result := TEnumerator&lt;T>.Create(\n          function: Boolean\n          begin\n            if Count &lt; N then\n            begin\n              Result := Enumerator.MoveNext;\n              Inc(Count);\n            end\n            else\n              Result := False;\n          end\n        );\n      end\n    )\n  );\nend;\n\nfunction TIteratorWrapper&lt;T>.ToArray: TArray&lt;T>;\nvar\n  Enumerator: TEnumerator&lt;T>;\n  List: TList&lt;T>;\nbegin\n  List := TList&lt;T>.Create;\n  try\n    Enumerator := FEnumerable.GetEnumerator;\n    while Enumerator.MoveNext do\n      List.Add(Enumerator.Current);\n    Result := List.ToArray;\n  finally\n    List.Free;\n  end;\nend;\n\nfunction TIteratorWrapper&lt;T>.GetEnumerator: TEnumerator&lt;T>;\nbegin\n  Result := FEnumerable.GetEnumerator;\nend;\n\n{ Helper functie }\nfunction From&lt;T>(Iterable: TEnumerable&lt;T>): TIteratorWrapper&lt;T>;\nbegin\n  Result := TIteratorWrapper&lt;T>.Create(Iterable);\nend;\n\nprocedure TestLazyIterator;\nvar\n  Numbers: TArray&lt;Integer>;\n  Result: TArray&lt;Integer>;\nbegin\n  Numbers := TArray&lt;Integer>.Create(1, 2, 3, 4, 5);\n\n  Result := From&lt;Integer>(TArray&lt;Integer>.Create(Numbers))\n    .Map(\n      function(X: Integer): Integer\n      begin\n        Result := X * 2;\n      end)\n    .Filter(\n      function(X: Integer): Boolean\n      begin\n        Result := X > 5;\n      end)\n    .Take(2)\n    .ToArray;\n\n  WriteLn('Resultaat: ', String.Join(', ', Result));  \/\/ Resultaat: 6, 8\nend;\n\nbegin\n  TestLazyIterator;\nend.\n<\/pre>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-8975","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts\/8975","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/comments?post=8975"}],"version-history":[{"count":1,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts\/8975\/revisions"}],"predecessor-version":[{"id":8976,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts\/8975\/revisions\/8976"}],"wp:attachment":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/media?parent=8975"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/categories?post=8975"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/tags?post=8975"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}