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SBASIC Manual - Page 29

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     SBasic User's Manual     SBasic Version 2.7             Page 29
     Printed:  December 5, 1999
     The FOR-NEXT structure creates an iterated loop.  This means that a
     selected variable, called the index variable, controls exactly how
     many times the loop is executed.  Control executes all statements
     between the FOR statement and the NEXT statement until the value in
     the index variable EXCEEDS a specified limit.  The index variable is
     always tested at the top of the loop.  The comparison is signed for
     the usual FOR-NEXT loop, although you can use an unsigned comparison
     if necessary.


          for n = 1 to 10
               a = a + n

     Here, the variable N starts with a value of one.  The statement inside
     the loop is executed ten times, with N incrementing each time the NEXT
     statement executes.  Eventually, N holds the value 11 when the FOR
     statement executes.  At this point, the statement inside the loop is
     not executed.  Instead, control passes directly to the statement
     following the NEXT statement.

     Sometimes you must use a limit larger than $7fff.  Since SBasic uses
     16-bit math, numbers larger than $7fff are treated as negative in
     signed comparisons.  Therefore, the following example:

          for n = 1 to $9000
               a = a + 1

     will exit immediately, as SBasic treats $9000 as a negative number,
     and 1 is already greater than a negative number.

     To change the above example to use an unsigned comparison, use the TO*
     operator.  The above example becomes:

          for n = 1 to* $9000
               a = a + 1

     This loop will execute the expected $9000 times.

     Remember to leave room on your limit value so that the index variable
     can actually exceed the limit.  For example:

          for n = 1 to* $ffff
               a = a + 1

     This loop will never end, since the value of N can never exceed the
     limit of $ffff.