Re: [fpc-pascal] Record Constructors which differ in parameter lists
On Fri, 12 May 2023, Thomas Kurz via fpc-pascal wrote: I would expect the type helper to remain functional. The types are the same for all purposes except they have a different RTTI entry. But this behaviour seems inconsistent to me. For example: With "var x:double" I can use "x.IsNan". With TDateTime, which is defined as "type TDateTime = type Double", I cannot. With strings, I can use "x.IsEmpty". With Utf8String, which is defined as "type TUtf8String = type AnsiString", I cannot. It's not because I expect it to, that it is actually so. As I said, Sven will need to explain what the current behaviour actually is... Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Record Constructors which differ in parameter lists
> I would expect the type helper to remain functional. The types are the same > for all purposes except they have a different RTTI entry. But this behaviour seems inconsistent to me. For example: With "var x:double" I can use "x.IsNan". With TDateTime, which is defined as "type TDateTime = type Double", I cannot. With strings, I can use "x.IsEmpty". With Utf8String, which is defined as "type TUtf8String = type AnsiString", I cannot. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Record Constructors which differ in parameter lists
On Wed, 10 May 2023, Thomas Kurz via fpc-pascal wrote: Dear Michael, thank you for the explanation. I understand that the helper overwrites the original constructor. But... I have defined "type TSomething = type TVec3f" (note the second "type"). So from my perspective, I'd assume that the TSomethingHelper doesn't apply to TVec3f at all because TSomething is defined as a new type, not only an alias for TVec3f. I would expect the type helper to remain functional. The types are the same for all purposes except they have a different RTTI entry. But the exact behaviour of the compiler in this case is something that Sven Barth will need to explain... Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Record Constructors which differ in parameter lists
Dear Michael,
thank you for the explanation. I understand that the helper overwrites the
original constructor. But...
I have defined "type TSomething = type TVec3f" (note the second "type"). So
from my perspective, I'd assume that the TSomethingHelper doesn't apply to
TVec3f at all because TSomething is defined as a new type, not only an alias
for TVec3f.
- Original Message -
From: Michael Van Canneyt via fpc-pascal
To: Thomas Kurz via fpc-pascal
Sent: Tuesday, May 9, 2023, 23:55:47
Subject: [fpc-pascal] Record Constructors which differ in parameter lists
On Tue, 9 May 2023, Thomas Kurz via fpc-pascal wrote:
> Hello,
> let's take the following example:
> program Project1;
> {$MODE OBJFPC}
> {$MODESWITCH ADVANCEDRECORDS}
> {$MODESWITCH TYPEHELPERS}
> type TVec3f = record
> x, y, z: Double;
> constructor Create (a1, a2, a3: Double);
> end;
> type TSomething = type TVec3f;
> type TSomethingHelper = type helper for TSomething
> constructor Create (a1, a2: Double);
> end;
> constructor TVec3f.Create (a1, a2, a3: Double);
> begin
> Self.x := a1;
> Self.y := a2;
> Self.z := a3;
> end;
> constructor TSomethingHelper.Create (a1, a2: Double);
> begin
> Self.x := a1;
> Self.y := a2;
> Self.z := 1 - a1 - a2;
> end;
> var f: TVec3f;
> begin
> f := TVec3f.Create (0.0, 0.0, 0.0); // <-- error here
> end.
> I get the error:
> project1.lpr(35,37) Error: Wrong number of parameters specified for call to
> "Create"
> project1.lpr(25,30) Error: Found declaration: constructor
> Create(Double;Double);
> So, obviously, FPC tries to apply the helper of TSomething (which should be
> decoupled from TVec3f because of the "type TVec3f" declaration) to TVec3f
> which hasn't defined any constructor with 2 parameters.
> Is this intended behavior or should I report it as a bug?
This is intended behaviour since declarations in helpers always take
precedence over the methods in the class/record.
Try to add overload; to the constructor in the helper. This is a hint to the
compiler that it should look for other methods.
Michael.
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Re: [fpc-pascal] Record Constructors which differ in parameter lists
On Tue, 9 May 2023, Thomas Kurz via fpc-pascal wrote:
Hello,
let's take the following example:
program Project1;
{$MODE OBJFPC}
{$MODESWITCH ADVANCEDRECORDS}
{$MODESWITCH TYPEHELPERS}
type TVec3f = record
x, y, z: Double;
constructor Create (a1, a2, a3: Double);
end;
type TSomething = type TVec3f;
type TSomethingHelper = type helper for TSomething
constructor Create (a1, a2: Double);
end;
constructor TVec3f.Create (a1, a2, a3: Double);
begin
Self.x := a1;
Self.y := a2;
Self.z := a3;
end;
constructor TSomethingHelper.Create (a1, a2: Double);
begin
Self.x := a1;
Self.y := a2;
Self.z := 1 - a1 - a2;
end;
var f: TVec3f;
begin
f := TVec3f.Create (0.0, 0.0, 0.0); // <-- error here
end.
I get the error:
project1.lpr(35,37) Error: Wrong number of parameters specified for call to
"Create"
project1.lpr(25,30) Error: Found declaration: constructor Create(Double;Double);
So, obviously, FPC tries to apply the helper of TSomething (which should be decoupled
from TVec3f because of the "type TVec3f" declaration) to TVec3f which hasn't
defined any constructor with 2 parameters.
Is this intended behavior or should I report it as a bug?
This is intended behaviour since declarations in helpers always take
precedence over the methods in the class/record.
Try to add overload; to the constructor in the helper. This is a hint to the
compiler that it should look for other methods.
Michael.
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[fpc-pascal] Record Constructors which differ in parameter lists
Hello,
let's take the following example:
program Project1;
{$MODE OBJFPC}
{$MODESWITCH ADVANCEDRECORDS}
{$MODESWITCH TYPEHELPERS}
type TVec3f = record
x, y, z: Double;
constructor Create (a1, a2, a3: Double);
end;
type TSomething = type TVec3f;
type TSomethingHelper = type helper for TSomething
constructor Create (a1, a2: Double);
end;
constructor TVec3f.Create (a1, a2, a3: Double);
begin
Self.x := a1;
Self.y := a2;
Self.z := a3;
end;
constructor TSomethingHelper.Create (a1, a2: Double);
begin
Self.x := a1;
Self.y := a2;
Self.z := 1 - a1 - a2;
end;
var f: TVec3f;
begin
f := TVec3f.Create (0.0, 0.0, 0.0); // <-- error here
end.
I get the error:
project1.lpr(35,37) Error: Wrong number of parameters specified for call to
"Create"
project1.lpr(25,30) Error: Found declaration: constructor Create(Double;Double);
So, obviously, FPC tries to apply the helper of TSomething (which should be
decoupled from TVec3f because of the "type TVec3f" declaration) to TVec3f which
hasn't defined any constructor with 2 parameters.
Is this intended behavior or should I report it as a bug?
Versions used:
Lazarus 2.3.0 (rev main-2_3-3525-g9208f17734) FPC 3.3.1 i386-win32-win32/win64
(FPC is not the most recent build, it's about 2~3 weeks old)
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