Solved

BoolToStr causes Undeclared Identifier error

Posted on 2007-11-16
12
1,231 Views
Last Modified: 2010-04-21
I need to convert a boolean value to a string, but BoolToStr does not work. Why?

I'm using Delphi 5.0

Thanks,

J
0
Comment
Question by:JonathanGSK
  • 3
  • 2
  • 2
  • +3
12 Comments
 
LVL 19

Expert Comment

by:MerijnB
ID: 20300259
that is strange, BoolToStr is not really something difficult,

can you show some code?
0
 
LVL 18

Accepted Solution

by:
Johnjces earned 100 total points
ID: 20300489
I refreshed! :)

Delphi 5 does not have BoolToStr.

Here is a code snippet from Koders Code Search...

function BoolToStr(B: Boolean; UseBoolStrs: Boolean = False): string;
const
  cSimpleBoolStrs: array [boolean] of String = ('0', '-1');
begin
  if UseBoolStrs then
  begin
    VerifyBoolStrArray;
    if B then
      Result := TrueBoolStrs[0]
    else
      Result := FalseBoolStrs[0];
  end
  else
    Result := cSimpleBoolStrs[B];
end;

Their URL is:

http://www.koders.com/delphi/fid53147BF1A84109076F2982F8935A5A188DE37B0C.aspx

John
0
 
LVL 19

Expert Comment

by:MerijnB
ID: 20300517
and I didn't read the question thoroughly enough...

Johnjces posst looks good, I just wonder if TrueBoolStrs and FalseBoolStrs are available in D5?
0
Problems using Powershell and Active Directory?

Managing Active Directory does not always have to be complicated.  If you are spending more time trying instead of doing, then it's time to look at something else. For nearly 20 years, AD admins around the world have used one tool for day-to-day AD management: Hyena. Discover why

 
LVL 18

Expert Comment

by:Johnjces
ID: 20300601
MerijnB

I could not find it anywhere in my D5 install.

All of that is declared/defined in the  PXDelphi5.pas posted by Koders Code Search... same URL as above.

John
0
 
LVL 25

Expert Comment

by:imitchie
ID: 20303994
is it not easier to write your own?
function BoolToStr(B: Boolean): string;
const
  cTrueFalseString: array [boolean] of String = ('true', 'false'); // change this
begin
  Result := cSimpleBoolStrs[B];
end;

Open in new window

0
 
LVL 11

Expert Comment

by:ZhaawZ
ID: 20304174
imitchie, I think it should be  "(false, true)" :)

And I'd advise to use "if b then result := cTrueFalseString[true] else result := cTrueFalseString[false]", otherwise there could be situations when your function won't work:

var
    b : boolean;
begin
b := boolean(2);
ShowMessage(BoolToStr(b)); // your function; crashes
ShowMessage(SysUtils.BoolToStr(b, true)); // default D6's function; shows "true"
end;

"2" in "b := boolean(2)" could be result of some function which is not written by you, so such situations are possible.
0
 
LVL 45

Expert Comment

by:aikimark
ID: 20306368
somethings missing or altered from Koders snippet:

{ StrToBool converts the given string to a boolean value.  If the string
  doesn't contain a valid value, an EConvertError exception is raised.
  BoolToStr converts boolean to a string value that in turn can be converted
  back into a boolean.  BoolToStr will always pick the first element of
  the TrueStrs/FalseStrs arrays. }

var
  TrueBoolStrs: array of String;
  FalseBoolStrs: array of String;

const
  DefaultTrueBoolStr = 'True';   // DO NOT LOCALIZE
  DefaultFalseBoolStr = 'False'; // DO NOT LOCALIZE

function BoolToStr(B: Boolean; UseBoolStrs: Boolean = False): string;

procedure VerifyBoolStrArray;
begin
  if Length(TrueBoolStrs) = 0 then
  begin
    SetLength(TrueBoolStrs, 1);
    TrueBoolStrs[0] := DefaultTrueBoolStr;
  end;
  if Length(FalseBoolStrs) = 0 then
  begin
    SetLength(FalseBoolStrs, 1);
    FalseBoolStrs[0] := DefaultFalseBoolStr;
  end;
end;

function BoolToStr(B: Boolean; UseBoolStrs: Boolean = False): string;
const
  cSimpleBoolStrs: array [boolean] of String = ('0', '-1');
begin
  if UseBoolStrs then
  begin
    VerifyBoolStrArray;
    if B then
      Result := TrueBoolStrs[0]
    else
      Result := FalseBoolStrs[0];
  end
  else
    Result := cSimpleBoolStrs[B];
end;
0
 
LVL 25

Expert Comment

by:imitchie
ID: 20306498
zhaawz, i learned something new today!  I have refined the function

i never knew
var b: boolean
b := Boolean(2) is valid!
function BoolToStr(B: Boolean): string;
const
  cTrueFalseString: array [boolean] of String = ('false', 'true'); // change this
begin
  if B then
    Result := cTrueFalseString[false]
  else
    Result := cTrueFalseString[true];
end;

Open in new window

0
 
LVL 25

Expert Comment

by:imitchie
ID: 20306502
except.. it is true =0, false=1
cos i debugged it
function BoolToStr(B: Boolean): string;
const
  cTrueFalseString: array [boolean] of String = ('true', 'false'); // change this
begin
  if B then
    Result := cTrueFalseString[false]
  else
    Result := cTrueFalseString[true];
end;

Open in new window

0
 
LVL 11

Expert Comment

by:ZhaawZ
ID: 20306766
"except.. it is true =0, false=1"

if 0, then false, otherwise true ;) it has been like that for many years.


>> begin
>>   if B then
>>     Result := cTrueFalseString[false]
>>   else
>>     Result := cTrueFalseString[true];
>> end;

why do you return false on "if b"? "if b" is the same as "if b = true", so if it's true, you're returning "false" string, but if it's false, you're returning "true" string.
0
 
LVL 45

Expert Comment

by:aikimark
ID: 20308045
In Delphi, False and True are an enumeration of a boolean set.  As such, they have implied numeric values that are indexes into their positions in the [False, True] set.
0
 

Author Closing Comment

by:JonathanGSK
ID: 31409596
Thanks to everyone who contributed to a VERY thorough analysis of this problem. John's answer is correct - I guess it's time to upgrade to Delphi7!

I have been using a very inelegant line, which works:

if Flag=True then String1:='True' else String1:='False';

But thanks for the alternatives,

Jonathan
0

Featured Post

Master Your Team's Linux and Cloud Stack!

The average business loses $13.5M per year to ineffective training (per 1,000 employees). Keep ahead of the competition and combine in-person quality with online cost and flexibility by training with Linux Academy.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Creating an auto free TStringList The TStringList is a basic and frequently used object in Delphi. On many occasions, you may want to create a temporary list, process some items in the list and be done with the list. In such cases, you have to…
In my programming career I have only very rarely run into situations where operator overloading would be of any use in my work.  Normally those situations involved math with either overly large numbers (hundreds of thousands of digits or accuracy re…
This Micro Tutorial will give you a basic overview how to record your screen with Microsoft Expression Encoder. This program is still free and open for the public to download. This will be demonstrated using Microsoft Expression Encoder 4.
Two types of users will appreciate AOMEI Backupper Pro: 1 - Those with PCIe drives (and haven't found cloning software that works on them). 2 - Those who want a fast clone of their boot drive (no re-boots needed) and it can clone your drive wh…

770 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question