For Loops

Syntax#

• for OrdinalVariable := LowerOrdinalValue to UpperOrdinalValue do begin {loop-body} end;
• for OrdinalVariable := UpperOrdinalValue downto LowerOrdinalValue do begin {loop-body} end;
• for EnumerableVariable in Collection do begin {loop-body} end;

Remarks#

• Delphi’s for-loop syntax does not provide anything to change step amount from 1 to any other value.
• When looping with variable ordinal values, e.g. local variables of type Integer, the upper and lower values will be determined only once. Changes to such variables will have no effect on the loops iteration count.

Simple for loop

A for loop iterates from the starting value to the ending value inclusive.

program SimpleForLoop;

{$APPTYPE CONSOLE}

var
  i : Integer;
begin
  for i := 1 to 10 do
    WriteLn(i);
end.

Output:

1
2
3
4
5
6
7
8
9
10

Looping over characters of a string

The following iterates over the characters of the string s. It works similarly for looping over the elements of an array or a set, so long as the type of the loop-control variable (c, in this example) matches the element type of the value being iterated.

program ForLoopOnString;

{$APPTYPE CONSOLE}

var
  s : string;
  c : Char;
begin
  s := 'Example';
  for c in s do
    WriteLn(c);
end.

Output:

E
x
a
m
p
l
e

Reverse-direction for loop

A for loop iterates from the starting value down to the ending value inclusive, as a “count-down” example.

program CountDown;

{$APPTYPE CONSOLE}

var
  i : Integer;
begin
  for i := 10 downto 0 do
    WriteLn(i);
end.

Output:

10
9
8
7
6
5
4
3
2
1
0

For loop using an enumeration

A for loop iterate through items in an enumeration

program EnumLoop;

uses
  TypInfo;

type
  TWeekdays = (Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday);

var
  wd : TWeekdays;
begin

  for wd in TWeekdays do
    WriteLn(GetEnumName(TypeInfo(TWeekdays), Ord(wd)));

end.

Output:

Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday

For in array

A for loop iterate through items in an array

program ArrayLoop;
{$APPTYPE CONSOLE}  
const a : array[1..3] of real = ( 1.1, 2.2, 3.3 );
var f : real;
begin
  for f in a do
    WriteLn( f );    
end.

Output:

1,1
2,2
3,3