Drivers: GetPositionAhead

       Name: GetPositionAhead                                        [Show more]
       Type: Subroutine
   Category: Drivers
    Summary: Decrement X to the previous position number (from 19 to 0 and
             round again), which gives the position ahead of X
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * MoveAndDrawCars calls GetPositionAhead
             * ProcessOvertaking (Part 1 of 3) calls GetPositionAhead
             * SetDriverSpeed calls GetPositionAhead
             * SetPlayerPositions calls GetPositionAhead


.GetPositionAhead

 DEX                    \ Decrement X

 BPL prev1              \ If X is >= 0, jump to prev1 to skip the following
                        \ instruction

 LDX #19                \ Set X = 19, so repeated calls to this routine will
                        \ decrement X down to 0, and then start again at 19

.prev1

 RTS                    \ Return from the subroutine