`For` Statement

Runs a block of statements for all numbers in a range.

Syntax

For counter [ As type ] = start_value To end_value [ Step step_value ]
    [ statements ]
End [ For [ counter ] ]

Parts

counter: Mandatory in the line that starts with For. It declares an integer variable.; Optional in the line that starts with End
type: Optional data type of counter. Permitted types include: Int8, Int16, Int32, Int64, Int128, UInt8, UInt16, UInt32, UInt64, and UInt128.
start_value: Mandatory integer expression. It becomes the initial value of counter.
end_value: Mandatory integer expression. It can become the last value of counter before the loop stops.
step_value: Optional integer expression. It is added to counter after each time through the loop. The default is one (1).
statements: Optional one or more statements between For and End. They run for each value between start_value and end_value.; The alternative is two or more groups of statements. The initial group starts with Exit When, and runs the same as given above. The subsequent groups start with When, and run when (1) the loop cannot start, or (2) after the loop stops. See § When statements for more information.
End: Completes the statement. You can also use End For. The optional variable counter can only follow End For.; You can change the syntax of this part. See § Changes in syntax with @Option for more information.

Instructions

You can use For when you want to run a sequence of statements again and again. It is recommended when you can be sure how many times the statements must run. Control is connected with the variable counter specified in the line that starts with For. Other loop constructs are possibly more flexible. See § See also below for more information.

In the example that follows, the variable index starts with a Value of one (1). Its Value increases by one each time through the loop. The loop stops after the Value of index gets to 5.

For index = 1 To 5
    #Debug.Print $"{index} "
End For
#Debug.PrintLine
' Output: 1 2 3 4 5

The next example simulates the countdown for the launch of a spacecraft. It starts at 10 and goes down to one, with a one second pause after each iteration. The clause Step -1 causes the Value of countdown to decrease by one.

For countdown = 10 To 1 Step -1
    #Debug.PrintLine countdown
    Sleep 1000 ' milliseconds
End For
#Debug.PrintLine "BLASTOFF!"

Usual operation

When this type of loop starts, ViviFire calculates start_value, end_value, and step_value. ViviFire calculates these values only one time and assigns counter the value of start_value.

Before the statement block runs, ViviFire compares counter to end_value. If it is less than or equal to end_value and step_value is greater than zero, the loop runs. And if it is greater than or equal to end_value and step_value is less than zero, the loop runs. But if the two conditions are false, the loop does not run and control moves to the statement after End.

Each time ViviFire gets to End, it adds step_value to counter and goes back to For. Again it compares counter to end_value, and again it runs the block or stops the loop as a result. This process continues until counter becomes out-of-range of end_value. Alternatively, one of the statements Exit or Return can stop the loop.

`step`

step_value can be positive or negative. The value of this expression selects how the loop runs as follows:

`Step`
Value	What the loop does
Greater than zero	Runs while `counter` <= `end_value`
Less than zero	Runs while `counter` >= `end_value`
Zero	Raises the exception `RangeError`

If you do not supply step_value, its default value is 1.

Counter

The variable counter is always locally scoped to the loop body.
This variable cannot have the same name as a different (unqualified) variable that is available in the same scope.
The variable must have an integer data type.
You are not permitted to change the value of the variable directly.

`Exit For`

The statement Exit For can stop this type of loop. Exit For immediately moves control to the statement after End.

Exit can also stop more than one nested loop. You can use the statement «Exit For, For» in the inner loop to stop two loops.

When statements

To find if a loop of this type completed because counter became more than end_value, use When DONE.

To find if a loop of this type did not run because counter was initially out-of-range, use When NONE.

See Exit When Clause for more information.

Changes in syntax with `@Option`

There are two areas where you can chage the syntax of the statement:

@Option End Block and @Option End
@Option End For ID and @Option End For

See @Option Directive for more information.

Examples

TODO

For Statement