On Fri, Jul 25, 2003 at 04:30:35PM +0200, Florian Klaempfl wrote: > James Mills wrote: > >On Fri, Jul 25, 2003 at 04:21:36PM +0200, Jonas Maebe wrote: > > > >>On vrijdag, jul 25, 2003, at 16:22 Europe/Brussels, James Mills wrote: > >> > >> > >>>Why does the following result in a runtime error ? > >>> > >>>program example; > >>> > >>>const > >>> THE_PORT = 9999; > >>> > >>>function swapWord(w: Word): Word; > >>>begin > >>> swapWord := (w SHL 8) OR (w SHR 8); > >>>end; > >> > >>In Pascal, all calculations are performed using the base type (which is > >>longint in FPC), so if w > 255, then w shl 8 > high(word) and will > >>result in a range check error when assigning to swapWord. Even if we > >>calculated everything using words, you'd still get an overflow error, > >>this time when doing the shl. > > > > > >How can I correct this ? > >This bit of code was taken directly from server.pp in one of the old > >2002 mailing threads... > > Turn range checking off for this piece of code or do > > function swapWord(w: Word): Word; > begin > swapWord := ((w SHL 8) OR (w SHR 8)) and $ffff; > end;
Least now I know the reason :) cheers James > > > _______________________________________________ > fpc-pascal maillist - [EMAIL PROTECTED] > http://lists.freepascal.org/mailman/listinfo/fpc-pascal -- - -Zero Defect Software Engineers Group - ZDSEG - -You need only two tools. WD-40 and duct tape. -If it doesn't move and it should, use WD-40. -If it moves and shouldn't, use the tape. _______________________________________________ fpc-pascal maillist - [EMAIL PROTECTED] http://lists.freepascal.org/mailman/listinfo/fpc-pascal
