ThinBASIC Core Language > Program Flow

Description

Executes all the statements between FOR and NEXT keywords by a number of times defined by Counter. Counter is automatically incremented at every iteration.

Syntax

For Counter [ AS AnyNumericType] = nStart TO nStop [Step Increment] [{While | Until | When} LogicalExpression]

...

{statements}

[Exit For]

[Iterate For]

{statements}

...

Next [Counter]

<< In thinBasic it is not necessary to indicate counter variable into Next statement. If present it will just be skipped.

Returns

Parameters

Name	Meaning
Counter	is a numeric variable controlling the iteration. Counter variable can be created on the fly adding the optional AS clause followed by any of the basic numeric types available in thinBasic
nStart	is a numeric expression that determine the first value assigned to Counter
nStop	is a numeric expression that determine the value at which the loop will stop
Increment	is an optional numeric expression that will determine the amount of which Counter will be incremented/decremented at every iteration
LogicalExpression	Is an optional logical expression valuated as zero (%FALSE) or not zero (%TRUE) connected with WHILE or UNTIL or When clause to the main FOR/NEXT loop. If present, at every FOR/NEXT iteration such expression will be evaluated and compared with the WHILE \| UNTIL \| When clause in order to check its validity. FOR/NEXT loop will terminate if Counter will reach nStop limit or WHILE \| UNTIL clause will be true. FOR/NEXT loop will iterate if Counter has not reached nStop limit and With clause will be FALSE.

Remarks

Every time a NEXT keyword is encountered, the corresponding Counter variable is incremented (or decremented) by Increment, if present, or by 1 if Increment is not present.

If LogicalExpression is present, it is evaluated before Counter variable will be incremented, permitting precise control over loop termination.

To exit from a FOR/NEXT loop use EXIT FOR clause. To exit from nested FOR/NEXT, multiple EXIT ... FOR can be used, one for each nesting level.

For example to exit from a 2 level FOR/NEXT use EXIT EXIT FOR. See below example.

At the end of a FOR / NEXT loop, Counter variable will be equal to (Stop + Increment), in case of positive Increment, or (Stop - Increment), in case of negative Increment.

If EXIT FOR is fired during a FOR / NEXT loop, at the end of the loop, Counter will have the value present just before the EXIT LOOP.

Restrictions

Counter variable after the NEXT keyword is permitted for compatibility issues with other BASIC dialects but it is just ignored by parser. You can place whatever after the NEXT statement just be aware parser will ignore it.