| Description |
The Not keyword is used in two different ways:
1. To perform a logical or boolean 'Not' of a logical value.If True, the value becomes False. If False, the value becomes True.
2. To perform a mathematical 'Not' of an integer in a bitwise fashion. The result is a bitwise 'Not' of the number - every bit value is reversed - 0 to 1 and 1 to 0.
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| Notes |
If the boolean expression is calculated (as opposed to being a Boolean variable), then brackets are required to isolate it.
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| Related commands |
| And |
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Boolean and or bitwise and of two arguments |
| Boolean |
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Allows just True and False values |
| If |
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Starts a conditional expression to determine what to do next |
| Or |
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Boolean or or bitwise or of two arguments |
| Xor |
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Boolean Xor or bitwise Xor of two arguments |
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| Example code : Illustrate both types of Not usage |
// Full Unit code.
// -----------------------------------------------------------
// You must store this code in a unit called Unit1 with a form
// called Form1 that has an OnCreate event called FormCreate.
unit Unit1;
interface
uses
SysUtils,
Forms, Dialogs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm} // Include form definitions
procedure TForm1.FormCreate(Sender: TObject);
var
num1, num2 : Word;
begin
num1 := $2C; // Binary value : 0000 0000 0010 1100
// Not'ed value : 1111 1111 1101 0011 = $FFD3
// And used to return a Boolean value
if Not (num1 > 0)
then ShowMessage('num1 <= 0')
else ShowMessage('num1 > 0');
// And used to perform a mathematical NOT operation
num2 := Not num1;
// Display the result
ShowMessage('Not $2C = $'+IntToHex(num2,2));
end;
end.
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| Hide full unit code |
num1 > 0
Not $2C = $FFD3
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