Re: [fpc-pascal] Case statement for class introspection
> On Jan 15, 2022, at 8:30 AM, Michael Van Canneyt via fpc-pascal
> wrote:
>
>> I saw a new syntax in Swift which I thought was clever and fits a pattern
>> I've seen before. Basically it's a case statement for class types which
>> lets you branch depending on which class type the class instance is at run
>> time.
>
> I think Scala did it before Swift.
What did it look like? Seems like an obvious feature any OOP language should
have.
Swift has a compound switch statement which does lots of things. It's a little
messy but it accomplishes this well. For example here they have a "case is" and
"case let _ as" which tests for class type or casts to a local variable using
"as".
switch object {
case is Message:
break
case let content as MessageContent:
break
case let attachment as Attachment:
break
default: break
}
Problem for Pascal is how to handle the casting mess. C languages (and Delphi
now I guess) can do inline variable declarations to avoid the casting.
Come to think of it this a similar problem with for-loops where you want to
loop over a collection of only certain types. For example:
for monster in monsters do
if monster is TZenChan then
TZenChan(monster).Dothis;
Swift does something similar as the switch which would look kind of like this:
for case monster as TZenChan in monsters do
TZenChan(monster).Dothis;
That syntax is not so nice but I like they're trying to help us manage class
introspection using existing language constructs.
Regards,
Ryan Joseph
___
fpc-pascal maillist - fpc-pascal@lists.freepascal.org
https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Case statement for class introspection
On Sat, 15 Jan 2022, Ryan Joseph via fpc-pascal wrote: I saw a new syntax in Swift which I thought was clever and fits a pattern I've seen before. Basically it's a case statement for class types which lets you branch depending on which class type the class instance is at run time. I think Scala did it before Swift. I wonder if this could be implemented in FPC? The syntax would be kind of clumsy though since you can't declare scoped variables in Pascal so you would need to do lots of casts but it's still cleaner than the equivalent code as if statements. This idea has been proposed before by Izak Maciej. I'm all for it. Michael. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
[fpc-pascal] Case statement for class introspection
I saw a new syntax in Swift which I thought was clever and fits a pattern I've seen before. Basically it's a case statement for class types which lets you branch depending on which class type the class instance is at run time. I wonder if this could be implemented in FPC? The syntax would be kind of clumsy though since you can't declare scoped variables in Pascal so you would need to do lots of casts but it's still cleaner than the equivalent code as if statements. = case monster of TZenChan: TZenChan(monster).DoThis; TPulPul: TPulPul(monster).DoThat; otherwise monster.DoSomething; end; Regards, Ryan Joseph ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] StrToInt is using ShortString buffer?
That is another reason for PChar based inner func. :) the input might be
Re: [fpc-pascal] StrToInt is using ShortString buffer?
Hi, I don’t see what the problem with a shortstring buffer is.. strtoint could not make use of an input string longer than 256 characters anyway, because the output integer could not have more than 19 digits anyway.. so an input string longer than this would be useless… just convert to a shortstring and to strtoint. the input might be
Re: [fpc-pascal] Crash on Windows for Aarch64 target
On 12-1-2022 14:37, Volo Zyko via fpc-pascal wrote: Hello, Some time ago it was announced an experimental support for Windows on Aarch64 (namely in this post https://lists.freepascal.org/pipermail/fpc-pascal/2020-April/057762.html). I tried to build a dll with a proprietary code for that target. Building succeeded but it crashes on loading. At the moment I don't understand how to investigate the issue to provide more information about it. I've been experimenting with this too. It looked cool to me to see if I can show our flagship product running on a rpi4. The major pain is to debug windbg what is going wrong on asm level. One of the issues I ran into was something weird when a case jumptable was used. It jumped to invalid code. I never was able to reproduce this in a smaller example and in the full code it was one of the issues it could run into. Now that VisualStudio starts to supports more and more dwarf debug info, I hope one day to use it as debugger. Marc ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-pascal
