Re: [fpc-pascal] For..in enumerator for generic records?
On 02.12.2016 08:22, Ryan Joseph wrote:
> Yes but the problem is doing this with generics. :) That’s where I got stuck
> and I don’t think it’s possible.
Ah, yes, right, sorry. Attached is a corrected version :)
Regards,
Sven
program trecenum;
{$mode objfpc}
{$modeswitch advancedrecords}
type
generic TRec = record
public type
TArrayType = array of T;
TEnumerator = object
private
fArr: TArrayType;
fIndex: Integer;
function GetCurrent: T;
public
constructor Create(aArr: TArrayType);
function MoveNext: Boolean;
property Current: T read GetCurrent;
end;
public
arr: TArrayType;
function GetEnumerator: TEnumerator;
end;
constructor TRec.TEnumerator.Create(aArr: TArrayType);
begin
fArr := aArr;
fIndex := -1;
end;
function TRec.TEnumerator.GetCurrent: T;
begin
Result := fArr[fIndex];
end;
function TRec.TEnumerator.MoveNext: Boolean;
begin
Inc(fIndex);
Result := fIndex < Length(fArr);
end;
function TRec.GetEnumerator: TRec.TEnumerator;
begin
Result.Create(Self.arr);
end;
type
TRecLongInt = specialize TRec;
TRecString = specialize TRec;
var
rl: TRecLongInt;
rs: TRecString;
i: LongInt;
s: String;
begin
rl.arr := TRecLongInt.TArrayType.Create(42, 53, 96, 29);
rs.arr := TRecString.TArrayType.Create('Alpha', 'Beta', 'Gamma', 'Delta');
for i in rl do
Writeln(i);
for s in rs do
Writeln(s);
end.
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Re: [fpc-pascal] For..in enumerator for generic records?
Yes but the problem is doing this with generics. :) That’s where I got stuck and I don’t think it’s possible. > On Dec 2, 2016, at 4:58 AM, Sven Barth wrote: > > I've attached an example that shows how this *can* be done (it's not the > only way to do this however). Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
On 30.11.2016 12:36, Ryan Joseph wrote:
>
>
>> On Nov 30, 2016, at 6:24 PM, Graeme Geldenhuys
>> wrote:
>>
>> What would you iterate/enumerate in that? I can understand iterating an
>> "array of TMyRec", but not TMyRec itself.
>
> I have a dynamic array inside a record. I’m using a record instead of a class
> because I want it to be stored on the stack. It’s trivial to just enumerate
> the array inside the record but I wanted to try the more elegant solution of
> making an enumerator for the record.
I've attached an example that shows how this *can* be done (it's not the
only way to do this however).
Regards,
Sven
program trecenum;
{$mode objfpc}
type
TLongIntArray = array of LongInt;
TRec = record
arr: TLongIntArray;
end;
TRecEnumerator = object
private
fArr: TLongIntArray;
fIndex: Integer;
function GetCurrent: LongInt;
public
constructor Create(aArr: TLongIntArray);
function MoveNext: Boolean;
property Current: LongInt read GetCurrent;
end;
constructor TRecEnumerator.Create(aArr: TLongIntArray);
begin
fArr := aArr;
fIndex := -1;
end;
function TRecEnumerator.GetCurrent: LongInt;
begin
Result := fArr[fIndex];
end;
function TRecEnumerator.MoveNext: Boolean;
begin
Inc(fIndex);
Result := fIndex < Length(fArr);
end;
operator enumerator(r: TRec): TRecEnumerator;
begin
Result.Create(r.arr);
end;
var
r: TRec;
i: LongInt;
begin
r.arr := TLongIntArray.Create(42, 53, 96, 29);
for i in r do
Writeln(i);
end.
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Re: [fpc-pascal] For..in enumerator for generic records?
> I just tried this really quick and it doesn’t seem to work with records but if I changed it to a class that worked. Just as you can't declare next field to be a record when learning linked list (well, we normally learned that some time in the past), the solution is just the same here: declare and use pointer to the record instead. Using classes, however, the pointer can be abstracted and you will have less messy code. -- View this message in context: http://free-pascal-general.1045716.n5.nabble.com/For-in-enumerator-for-generic-records-tp5726980p5726995.html Sent from the Free Pascal - General mailing list archive at Nabble.com. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
On Wed, 30 Nov 2016 18:24:11 +0700 Ryan Joseph wrote: >[...] I can wrap my head around nested types in classes because they’re >necessary for generics I just learned but nested classes feel messy. Is there >at least some namespace protection? Yes. And it follows visibility rules. > That would be a benefit I suppose if the class was only ever used > inside that class but a unit may be a better option in that case. Mattias ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
> On Nov 30, 2016, at 6:19 PM, Graeme Geldenhuys > wrote: > > Yeah, those were introduced in FPC 3.0.0 I believe - more Delphi > compatibility changes. I still don’t know if I like it though, but > understand its usage is meant if two classes are very close related. You > can now have nested classes (god knows how deep), constants, vars etc > all inside a class definition. The Delphi version of the Object Pascal > language is becoming pretty messy. Big mess indeed. I can wrap my head around nested types in classes because they’re necessary for generics I just learned but nested classes feel messy. Is there at least some namespace protection? That would be a benefit I suppose if the class was only ever used inside that class but a unit may be a better option in that case. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
> On Nov 30, 2016, at 6:22 PM, Marco van de Voort wrote: > > * (for..in) Enumerators in records Where’s an example of this? I’m trying it with a generic record and I can’t it to compile so I’m not sure if this is supported or not. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
> On Nov 30, 2016, at 6:24 PM, Graeme Geldenhuys > wrote: > > What would you iterate/enumerate in that? I can understand iterating an > "array of TMyRec", but not TMyRec itself. I have a dynamic array inside a record. I’m using a record instead of a class because I want it to be stored on the stack. It’s trivial to just enumerate the array inside the record but I wanted to try the more elegant solution of making an enumerator for the record. Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
On 2016-11-30 11:22, Marco van de Voort wrote: > D2006/ FPC 2.6.0 Thanks for the correction Marco. Wow, that long ago already. Regards, Graeme ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
On 2016-11-30 04:03, Ryan Joseph wrote: > I have a generic record I would like to enumerate using for..in loops. Maybe generics are redefining this, but a record (as I understand it) is something like TMyRec = record StrField: string; IntField: integer; BoleanField: boolean; end; What would you iterate/enumerate in that? I can understand iterating an "array of TMyRec", but not TMyRec itself. Regards, Graeme -- fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal http://fpgui.sourceforge.net/ My public PGP key: http://tinyurl.com/graeme-pgp ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
In our previous episode, Graeme Geldenhuys said: > Yeah, those were introduced in FPC 3.0.0 D2006/ FPC 2.6.0 from 2.6.0 release manifest: http://forum.lazarus.freepascal.org/index.php?topic=15656.0 * Delphi compatibility mode improvements * Nested types, class variables and class local constants * Advanced records syntax (no constructors yet) * (for..in) Enumerators in records * Class and record helpers * Generic records, arrays and procedural types * Delphi-compatibility of generics improved * Scoped enumerations * Custom messages for "deprecated" directive * Ability to use "&" for escaping keywords ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
On 2016-11-30 10:53, Ryan Joseph wrote: > There’s a class nested inside a class?? I never saw that before. Yeah, those were introduced in FPC 3.0.0 I believe - more Delphi compatibility changes. I still don’t know if I like it though, but understand its usage is meant if two classes are very close related. You can now have nested classes (god knows how deep), constants, vars etc all inside a class definition. The Delphi version of the Object Pascal language is becoming pretty messy. Regards, Graeme -- fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal http://fpgui.sourceforge.net/ My public PGP key: http://tinyurl.com/graeme-pgp ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
There’s a class nested inside a class?? I never saw that before. What are all the inlines for btw? > On Nov 30, 2016, at 3:09 PM, Sven Barth wrote: > > Take a look at packages/fcl-stl/src/gvector.pp, it's a generic vector > container that provides an enumerator. > > Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
I just tried this really quick and it doesn’t seem to work with records but if I changed it to a class that worked. Maybe I should use an object instead so it’s stored on the stack like a record? Not very important it can enumerate but I wanted to try first. > On Nov 30, 2016, at 5:53 PM, Ryan Joseph wrote: > > There’s a class nested inside a class?? I never saw that before. What are all > the inlines for btw? Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
Am 30.11.2016 05:35 schrieb "Ryan Joseph" : > > I have a generic record I would like to enumerate using for..in loops. Is this even possible? I tried briefly and it wasn’t clear this was possible so I thought I’d ask first. Thanks. > Take a look at packages/fcl-stl/src/gvector.pp, it's a generic vector container that provides an enumerator. Regards, Sven ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] For..in enumerator for generic records?
> I have a generic record I would like to enumerate using for..in loops. Is this even possible? I tried briefly and it wasn’t clear this was possible so I thought I’d ask first. Thanks. Take a look at how gvector implements it: http://svn.freepascal.org/svn/fpc/tags/release_3_0_0/packages/fcl-stl/src/gvector.pp -- View this message in context: http://free-pascal-general.1045716.n5.nabble.com/For-in-enumerator-for-generic-records-tp5726980p5726981.html Sent from the Free Pascal - General mailing list archive at Nabble.com. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
