[SOLVED] Bug in TryStrToInt??

[bonmario]

Hi,
view this code:

Code: Pascal  [Select][+][-]

1. var WrkNum:Integer;
2. begin
3.   WrkNum:=99;
4.   TryStrToInt('xd', WrkNum);
5.   ShowMessage(IntToStr(WrkNum));
6. end;
7.  

At the end of procedure, the value of "WrkNum" is "13".

It's a bug or i'm wrong?

Thanks in advance. Mario

[Handoko]

Sorry I was wrong. Please ignore this post.

No, it is not a bug.

The documentation does not say it will return any value for the out parameter i if the conversion failed:
https://www.freepascal.org/docs-html/rtl/sysutils/trystrtoint.html

You may expect to get 0, but no ... some may expect -1 if the function fails. So it is 'better' to not provide any expected value if it fails.

[avk]

Everything seems to be somewhat more interesting. d is the hexadecimal notation of 13. Try TryStrToInt ('x101', WrkNum).

[Zvoni]

Nevermind that TryStrToInt will return False if the conversion fails.
So why not just check the return-value of TryStrToInt?
If True (Conversion successful) use your Variable WrkNum, if False (Conversion failed), discard ANY value returned in WrkNum.

EDIT: Damn. I just noticed, that TryStrToInt returns True for the example.

[Zvoni]

Everything seems to be somewhat more interesting. d is the hexadecimal notation of 13. Try TryStrToInt ('x101', WrkNum).

'x101' returns 257 for me

[avk]

Yes, and TryStrToInt returns True.

[wp]

Well, in this case the conversion will even be successful as avk noted. Allowing hex numbers in C notation in Pascal is a bit surprising (instead of preceeding '$'), and allowing to start them with "x" instead of "0x" even more (at least to me as a non-C programmer). Is "xd" a valid C hex number? (or must it be "0xd"?) If not we have a bug here.

[EDIT]
Delphi accepts 'xd' as valid integer, too, and returns 13 like FPC.

[Zvoni]

Found it:
TryStrToInt uses the Val-Function
https://www.freepascal.org/docs-html/rtl/system/val.html

For hexadecimal values, the prefix '0x' or 'x' (case insensitive) may be used as well.

There it is: Your 'xd' is interpreted as a hexadecimal number and 'd' is a valid Hex-Symbol

[Thaddy]

Morons: 99 is already a number and not a string!!! And so the result is false. Programmer error....

Code: Pascal  [Select][+][-]

1. program untitled;
2. {$mode delphi}{$H+}
3. uses sysutils;
4. var WrkNum:Integer;
5. begin
6.   WrkNum:=99;
7.   if TryStrToInt('99', WrkNum) then
8.     writeln(IntToStr(WrkNum));
9. end.

[marcov]

Morons: 99 is already a number and not a string!!! And so the result is false. Programmer error....

So now read it again. That value is just to intialize the var in a test to show it is changed.

[Thaddy]

Well. read it again, Marco... Adapted typo..
TryStrToInt has no formatting, like Format(). Xd needs val() or the likes.
Probably means:

Code: Pascal  [Select][+][-]

1. {$mode delphi}{$H+}
2. uses sysutils;
3. var WrkNum:Integer;
4. begin
5.   WrkNum:=99;
6.   writeln(format('$%X', [WrkNum]));
7. end.

[avk]

There it is: Your 'xd' is interpreted as a hexadecimal number and 'd' is a valid Hex-Symbol

Well, yes, Cap said: reading documentation is always helpful.

[Thaddy]

This one? https://www.freepascal.org/docs-html/rtl/sysutils/trystrtoint.html
See above.

[avk]

Code: Pascal  [Select][+][-]

1. function TryStrToInt(const s: string; out i : Longint) : boolean;
2. var Error : word;
3. begin
4.   Val(s, i, Error);
5.   TryStrToInt:=Error=0
6. end;  
7.  

therefore it is useful to also see Val documentation.

[Thaddy]

Oh well, IntToStr causes it.....
This is simply not a bug...