BorlandTalk.com

Dennis · Guest

Hi

The poll

http://tech.groups.yahoo.com/group/fastcodeproject/surveys?id=12528539

will close in 3 days.

If the result becomes that we should support Non-Nil Zero Length Strings,
then we need to agree on some validation functions.

This validation creates a non nil string, sets the length field to zero,
adds a zero terminator at S[1] and validates that the empty string is
trimmed to an empty string. I think we all agree that this validation is
valid.

var
GlobalStrValidate16: AnsiString;

function TMainForm.Validate16 : Boolean;
var
S : string;
const
VALIDATENO : Cardinal = 16;

begin
Result := True;
GlobalStrValidate16 := #0;
PInteger(Integer(GlobalStrValidate16)-4)^ := 0; //Set Length to 0
S := TrimFunction(GlobalStrValidate16);
if S <> '' then
begin
ErrorTrap(VALIDATENO, GlobalStrValidate16);
Result := False;
Exit;
end;
end;

Best regards
Dennis Kjaer Christensen

Dennis · Guest

Hi

This validation creates a string = A#0, but with the length field set to
zero. The result of a Trim should be an empty string because the string is
length zero = empty. The current RTL Trim function passes the validation.

The question is whether this in general is a proper validation function for
Non-Nil Zero Length Strings.

var
GlobalStrValidate11: AnsiString;

function TMainForm.Validate11 : Boolean;
var
S : string;
const
VALIDATENO : Cardinal = 11;

begin
Result := True;
GlobalStrValidate11 := 'A';
PInteger(Integer(GlobalStrValidate11)-4)^ := 0; //Set Length to 0
S := TrimFunction(GlobalStrValidate11);
if S <> '' then
begin
ErrorTrap(VALIDATENO, GlobalStrValidate11);
Result := False;
Exit;
end;
end;

Best regards
Dennis Kjaer Christensen

Dennis · Guest

Hi

My personal opinion is that the validation is proper. I do not expect all
non-nil zero length strings to be zero terminated at index 1. These strings
are very non standard in the first place and I would be surprised if all
libraries creating them would put a zero terminator in the proper place. I
think we should validate against all kinds of non nil zero length strings
that the corresponding RTL function handles. I would like our functions to
behave as the RTL function they are meant to replace.

Best regards
Dennis Kjaer Christensen

Dennis · Guest

Hi

I need some help to formulate a proper poll question.

Best regards
Dennis Kjaer Christensen

Dennis · Guest

Hi

I have created a poll

http://tech.groups.yahoo.com/group/fastcodeproject/surveys?id=12540587

Best regards
Dennis Kjaer Christensen

Davy Landman · Guest

Hi,

I voted No because this validate functions doesn't check what the RTL
function does, it just checks if it returns an empty string ;)

Kind Regards,
Davy Landman

Dennis · Guest

Hi Davy

Davy Landman · Guest

Dennis · Guest

Hi Davy

We know that the Trim RTL function supports non nil .... strings and so must
our Trim functions. The validation simply tests this.

Run the validation and see the RTL function pass.

Conclusion: Your suggestion is valid, but not needed.

The real point of the discussion is what we discussed earlier. John said
that we should only validate against one Non-Nil Zero Length String - one
that is zero terminated at S[1].

I think we should valida against all Non-Nil Zero Length Strings that the
RTL function supports.

Best regards
Dennis Kjaer Christensen

Dennis · Guest

Hi

This Non-Nil Zero Length String validation is the only one that John finds
proper.

var
GlobalStrValidate16: AnsiString;

function TMainForm.Validate16 : Boolean;
var
S : string;
const
VALIDATENO : Cardinal = 16;

begin
Result := True;
GlobalStrValidate16 := #0;
PInteger(Integer(GlobalStrValidate16)-4)^ := 0; //Set Length to 0
S := TrimFunction(GlobalStrValidate16);
if S <> '' then
begin
ErrorTrap(VALIDATENO, GlobalStrValidate16);
Result := False;
Exit;
end;
end;

Best regards
Dennis Kjaer Christensen

Davy Landman · Guest

Ow, in that case, I'm waiting on arguments about that subject...

I misunderstood the question then..

Regards,
Davy

Aleksandr · Guest

Hi Dennis,

I try to continue Smile

My function creates an integer number=0 and calls Trim with @number+4.
The result of a Trim should be an empty string because the numbet=0.
The current RTL Trim function passes the validation. :-)

I think Validate11 is incorrect because it uses incorrect data.

--
regards,
Aleksandr

procedure TForm1.Button1Click(Sender: TObject);
var
i: integer;
p: pInteger;
s, t: string;
begin
i:=0;
p:=@i;
inc(p);
pointer(s):=p;
t:=Trim(s);
ShowMessage('*'+t+'*');
end;

Dennis · Guest

Hi Aleksandr

Aleksandr Sharahov · Guest

Hi Dennis,

Dennis · Guest

Hi Aleksandr