Difference between revisions of "For"
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| − | [[Keyword|keyword]] used with "[[to]]"\"[[downto]]" and "[[Do|do]]" | + | [[Keyword|keyword]] used with "[[to]]"\"[[downto]]" and "[[Do|do]]" to execute a loop in which the value of a control variable is incremented or decremented by 1 each time: |
| + | |||
| + | FOR ''control_variable'' := ''start'' to ''final'' do ''statement'' | ||
| + | which increases ''control_variable'' by 1 on each execution of the loop until the value is greater than or equal to ''final'' | ||
| + | or | ||
| + | for ''control_variable'' := ''start'' downto ''final'' do ''statement'' | ||
| + | which decreases ''control_variable'' by 1 on each execution of the loop until the value is less than or equal to ''final'' | ||
| + | |||
| + | Where ''control_variable'' is the variable to be set to the value of ''start''. The control variable is increased or decreased by 1 on each loop until its value reaches or exceeds ''final''. | ||
| + | |||
<delphi> | <delphi> | ||
| − | for I:=1 to 100 do | + | for I:=1 to 100 do ''statement''; |
</delphi> | </delphi> | ||
| − | (repeats | + | (repeats ''statement'' one hundred times, increasing I from 1 to 100) |
<delphi> | <delphi> | ||
| − | for I:=100 downto 1 | + | for I:=100 downto 1 do ''statement''; |
</delphi> | </delphi> | ||
| − | (repeats | + | (repeats ''statement'' one hundred times, decreasing I from 100 to 1) |
| + | |||
| + | * FOR will loop only the single statement that follows it. To execute more than one statement, enclose the group of statements in a [[Begin]]/[[End]] block. | ||
| + | * In a for..to loop, if ''start'' is greater than ''final'', the loop is not executed | ||
| + | * in a for..downto loop, if ''start'' is less than ''final'', the loop is not executed | ||
| + | |||
| + | After the loop, the value of ''control_variable'' will be ''final''. If the loop was not executed, the value of ''control_variable'' does not change. | ||
*you can use [[Type|types]] instead of numbers. | *you can use [[Type|types]] instead of numbers. | ||
{{Keywords}} | {{Keywords}} | ||
Revision as of 22:14, 26 October 2010
keyword used with "to"\"downto" and "do" to execute a loop in which the value of a control variable is incremented or decremented by 1 each time:
FOR control_variable := start to final do statement
which increases control_variable by 1 on each execution of the loop until the value is greater than or equal to final or
for control_variable := start downto final do statement
which decreases control_variable by 1 on each execution of the loop until the value is less than or equal to final
Where control_variable is the variable to be set to the value of start. The control variable is increased or decreased by 1 on each loop until its value reaches or exceeds final.
<delphi>
for I:=1 to 100 do statement;
</delphi> (repeats statement one hundred times, increasing I from 1 to 100)
<delphi>
for I:=100 downto 1 do statement;
</delphi> (repeats statement one hundred times, decreasing I from 100 to 1)
- FOR will loop only the single statement that follows it. To execute more than one statement, enclose the group of statements in a Begin/End block.
- In a for..to loop, if start is greater than final, the loop is not executed
- in a for..downto loop, if start is less than final, the loop is not executed
After the loop, the value of control_variable will be final. If the loop was not executed, the value of control_variable does not change.
- you can use types instead of numbers.
Keywords: begin — do — else — end — for — if — repeat — then — until — while
