Delphi Basics : For command

DelphiBasics

For
Keyword

Starts a loop that executes a finite number of times

1	keyword For(for Variable := Integer Expression to\|downto Integer Expression do Statement;
2	for Variable := Char Expression to\|downto Char Expression do Statement;
3	for Variable := Enum Expression to\|downto Enum Expression do Statement;

Description

The For keyword starts a control loop, which is executed a finite number of times.

The Variable is set to the result of the 1st Expression. If the result is less than or equal to the result of the 2nd Expression (when to is specified), then the Statement is executed. Variable is then incremented by 1 and the process is repeated until the variable value exceeds the 2nd expression value.

For downto, the variable value is checked as being greater than or equal to the 2nd expression, and its value is decremented at the loop end.

The Expressions may result in any Ordinal type - Integers, Characters or Enumerations.

The Statement maybe a single line, or a set of statements with a begin/end block.

Notes

The loop Variable value is not guaranteed by Delphi at loop end. So do not use it!

Related commands

Begin		Keyword that starts a statement block
Do		Defines the start of some controlled action
DownTo		Prefixes an decremental for loop target value
End		Keyword that terminates statement blocks
Repeat		Repeat statements until a ternmination condition is met
To		Prefixes an incremental for loop target value
Until		Ends a Repeat control loop
While		Repeat statements whilst a continuation condition is met

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Example code : Integer for loop

var
  i : Integer;

begin
  // Loop 5 times
  For i := 1 to (10 div 2) do
    ShowMessage('i = '+IntToStr(i));
end;

Show full unit code

  i = 1
  i = 2
  i = 3
  i = 4
  i = 5

Example code : Character for loop

var
  c : char;
begin
  // Loop 5 times - downwards
  For c := 'E' downto 'A' do
    ShowMessage('c = '+c);
end;

Show full unit code

  c = E
  c = D
  c = C
  c = B
  c = A

Example code : Enumeration for loop

var
  suit : (Hearts, Clubs, Diamonds, Spades);
begin
  // Loop 3 times
  For suit := Hearts to Diamonds do
    ShowMessage('Suit = '+IntToStr(Ord(suit)));
end;

Show full unit code

  Suit = 0
  Suit = 1
  Suit = 2