[DUG] Enable CheckBox

[David O'Brien]

I agree, it just makes me think about it rather than rush over it
assuming I know what I was thinking at the time. A personal thing. I
would hope that the compiler sorts it out the same either way...

 

From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz]
On Behalf Of Jolyon Smith
Sent: Tuesday, 27 April 2010 12:34 p.m.
To: 'NZ Borland Developers Group - Delphi List'
Subject: Re: [DUG] Enable CheckBox

 

Maybe it's just me, but "A doesn't equal B" surely reads more closely to
the real meaning than "not (A does equal B)".

 

Apart from anything else, the latter requires parentheses to avoid the
compiler getting confused and trying to do : "(Not A) equals (B)".  i.e.
the latter syntax is also to the compiler less close to the real meaning
(since it requires disambiguation).

 

>From a human perspective the scanning is more fluid:  A <> B, reads left
to right entirely as intended:  "A does not equal B".

 

NOT (A = B) on the other hand requires me to read it like a syntax tree
parser:  "NOT " ... (OK, store the fact that I have to logically invert
what follows, keep a mental note of parentheses) ... then what follows
is "( A is equal to B )" , right OK, so "A is equal to B inverted", i.e.
A does not equal B.

 

In other words, exactly what is menat literally and clearly when I
write... A <> B.

 

But as I say, maybe it's just me.

 

NOT (I think like a computer).

 

;)

 

From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz]
On Behalf Of David O'Brien
Sent: Tuesday, 27 April 2010 11:54 a.m.
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Enable CheckBox

 

Mainly because it makes me think about the real meaning when looking at
the code again J.

 

From: delphi-bounces at delphi.org.nz [mailto:delphi-bounces at delphi.org.nz]
On Behalf Of Colin Johnsun
Sent: Tuesday, 27 April 2010 11:47 a.m.
To: NZ Borland Developers Group - Delphi List
Subject: Re: [DUG] Enable CheckBox

 

I like David's version but why not get rid of the "not" to:

 

DBCheckBox4.Enabled := DBEdit2.Text <> '';

 

Cheers,

 

 

On 27 April 2010 09:40, Ian Drower <idrower at gmail.com> wrote:

Hi Bob
I'd use 
if DBEdit2.Text <> '' then
DBCheckBox4.Enabled := true
else
DBCheckBox4.Enabled := false

Ian




On 27/04/2010 10:52 a.m., David O'Brien wrote: 

	Why the four quotes in the false and a space in the true?

	 

	I would use something like:

	 

	DBCheckBox4.Enabled := not (DBEdit2.Text = '') ;

	 

	From: delphi-bounces at delphi.org.nz
[mailto:delphi-bounces at delphi.org.nz] On Behalf Of Bob Pawley
	Sent: Tuesday, 27 April 2010 10:39 a.m.
	To: NZ Borland Developers Group - Delphi List
	Subject: [DUG] Enable CheckBox

	 

	Hi

	 

	I am attempting to enable a checkbox only when a DBEdit has a
value. (Disabled when no string in DBEdit.)

	 

	Following is my code which disables the CheckBox after a delete
from the DBEdit.

	 

	But it is not enabled when I add a string to the DBEdit.

	------

	procedure TForm4.DBEdit2Change(Sender: TObject);
	begin

	 

	     if
	  DBEdit2.Text = ' '

	 

	  then
	  DBCheckBox4.Enabled := True

	 

	  Else if DBEdit2.Text = ''''

	 

	  then
	   DBCheckBox4.Enabled := False ;

	 

	end;

	 

	Thanks for any help.

	 

	Bob

	 
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