Array indexed by generic enum ?
lazarus / 62-General

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guest58172 · 2018-03-11 20:39

I feel a bit blocked because this is not accepted

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i type 
generic TFoo<SomeEnum> = class    a: array[SomeEnum] of integer; 
end;   TEnum = (e0, e1); var   a: specialize TFoo<TEnum>; 
Is this supported in a way or another ?

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bytebites · 2018-03-11 21:11

a: array[Low(SomeEnum)..High(SomeEnum)] of integer;

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guest58172 · 2018-03-11 21:15

This is what i'm trying to do in a helper record:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   generic
TEnumIndexedArray<TheEnum, ElementType> = record  private    fArray:
array[Low(TheEnum) .. High(TheEnum)] of ElementType;    procedure
setElement(index: TheEnum; value: ElementType);    function
getElement(index: TheEnum): ElementType;  public    property
element[index: TheEnum]: ElementType read getElement write setElement;
default;  end;  procedure TEnumIndexedArray.setElement(index: TheEnum;
value: ElementType);begin  fArray[integer(index)] :=
value;end; function TEnumIndexedArray.getElement(index: TheEnum):
ElementType;begin  result := fArray[integer(index)];end; 
but the compiler says: Error: Type mismatch

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guest58172 · 2018-03-11 21:33

I can use Byte boundaries but this not super nice, not strongly typed.
At least the ugly things are hidden.

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bytebites · 2018-03-12 03:12

It works in trunk-version.

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ASerge · 2018-03-12 18:02

Quote from: BBasile on March 11, 2018, 09:39:41 pmIs this supported in
a way or another ?
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
Project1;{$MODE OBJFPC}{$APPTYPE CONSOLE}{$MODESWITCH
ADVANCEDRECORDS} uses TypInfo; type  generic TEnumArray<TEnum, TData>
= record  private    FArray: array of TData;    FMinValue: LongInt;  
function GetItem(const Index: TEnum): TData; inline;    procedure
SetItem(const Index: TEnum; const Value: TData); inline;  public   
property Items[Index: TEnum]: TData read GetItem write SetItem;
default;    procedure Init;  end; function TEnumArray.GetItem(const
Index: TEnum): TData;begin  Result := FArray[LongInt(Index) -
FMinValue];end; procedure TEnumArray.Init;var  EnumTypeInfo:
PTypeInfo;  EnumTypeData: PTypeData;  i: LongInt;begin  EnumTypeInfo
:= TypeInfo(TEnum);  assert(EnumTypeInfo^.Kind = tkEnumeration,
'Support only enum types');  EnumTypeData :=
GetTypeData(EnumTypeInfo);  FMinValue := EnumTypeData^.MinValue; 
SetLength(FArray, EnumTypeData^.MaxValue - FMinValue + 1);  for i :=
Low(FArray) to High(FArray) do    FArray[i] :=
Default(TData);end; procedure TEnumArray.SetItem(const Index: TEnum;
const Value: TData);begin  FArray[LongInt(Index) - FMinValue] :=
Value;end; type  TOneTwoThree = (One, Two, Three);  TTwoThree =
Two..Three; var  X: specialize TEnumArray<TTwoThree,
TOneTwoThree>;begin  X.Init;  X[Two] := One;  X[Three] := X[Two]; 
Writeln(X[Three]);  Readln;end.

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Thaddy · 2018-03-20 07:44

In trunk it is even easier since last week, mantis 33414:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i {$mode
objfpc}{$H+}uses Classes, SysUtils; type  generic TFoo<SomeEnum> =
class    m: array[SomeEnum] of integer;  end;   TEnum = (e0, e1); var 
a: specialize TFoo<TEnum>; beginend.
But it needs trunk revision 38532 or higher. No need for typinfo.
It doesn't need a class. It also works for TArray<T>

Cleaned up code in proper syntax:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i {$mode
delphi} type  TFoo<SomeEnum> = class    m: array[SomeEnum] of
integer;  end;  TEnum = (e0, e1);var  a: TFoo<TEnum>;beginend.

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Thaddy · 2018-03-20 11:29

Quote from: ASerge on March 12, 2018, 07:02:19 pm
Cumbersome and slow. At least trunk works now...

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ASerge · 2018-03-21 00:39

Quote from: Thaddy on March 20, 2018, 12:29:32 pmCumbersome and slow.
At least trunk works now...
Yes, but it works!