Mega Code Archive
Pred - decrement an ordinal variable system unit
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function Pred ( const Ordinal Value ) : Ordinal type;
Description
The Pred function decrements an ordinal value, and returns this value.
You can decrement :
Characters
Non-floating number types
Enumeration types
Pointers
The decrement is by the base size of the unit. For example, decrementing a Pointer will be by 4 bytes if the pointer points to Words.
Notes
Pred is equivalent in performance to simple subtraction, or the Dec procedure.
Related commands
Dec Decrement an ordinal variable
Inc Increment an ordinal variable
Sqr Gives the square of a number
Sqrt Gives the square root of a number
Succ Increment an ordinal variable
Sum Return the sum of an array of floating point values
Example code : Decrementing characters, numbers and enumerations
type
TSuit = (Hearts, Clubs, Diamonds, Spades);
var
Character : char;
Number : Integer;
Card : TSuit;
begin
// We can decrement characters
Character := 'B';
ShowMessage('Character : '+Character);
Character := Pred(Character);
ShowMessage('Character-1 : '+Character);
// We can decrement numbers
Number := 23;
ShowMessage('Number : '+IntToStr(Number));
Number := Pred(Number);
ShowMessage('Number-1 : '+IntToStr(Number));
// We can decrement enumerations
Card := Clubs;
ShowMessage('Card starts at Clubs');
Card := Pred(Card);
if Card = Hearts then ShowMessage('Card is now Hearts');
if Card = Clubs then ShowMessage('Card is now Clubs');
if Card = Diamonds then ShowMessage('Card is now Diamonds');
if Card = Spades then ShowMessage('Card is now Spades');
end;
Show full unit code
Character : B
Character-1 : A
Number : 23
Number-1 : 22
Card starts at Clubs
Card is now Hearts
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