From: tr.17687@z991.linuxsc.com   
      
   Richard Harnden  writes:   
      
   > On 28/11/2022 15:30, Tim Rentsch wrote:   
   >   
   >> Richard Harnden  writes:   
   >>   
   >>> On 21/11/2022 20:45, Ben Bacarisse wrote:   
   >>>   
   >>>> I wonder if there are any real posters here?  Let's see...   
   >>>>   
   >>>> I came across a trivial programming task that must have been   
   >>>> solved a thousand times by other programmers, but it had never   
   >>>> crossed my path until yesterday.  I must be feeling my age   
   >>>> because I made a real hash of tackling it at first.  Anyway, I   
   >>>> thought it might be of interest.   
   >>>>   
   >>>> Consider any ordered measure that "wraps round" -- bearings in   
   >>>> degrees, minutes in the hour, indeed hours in either the 12 or 24   
   >>>> hour clock.  The problem is to determine if a given value is in   
   >>>> the sub-range specified by a start and an en value.   
   >>>>   
   >>>> I was specifically concerned with integer values where the   
   >>>> sub-range includes the start value but excludes the end value.   
   >>>> [...]   
   >>>   
   >>> I think this works ...   
   >>>   
   >>> int in_subrange(int range, int start, int end, int check)   
   >>> {   
   >>>      check %= range;   
   >>>   
   >>>      if (  ( end < start && (   
   >>>                 (check >= 0 && check <= end)   
   >>>              || (check >= start && check < range)   
   >>>              )   
   >>>            )   
   >>>         || ( check >= start && check <= end )   
   >>>         )   
   >>>              return 1;   
   >>>   
   >>>      return 0;   
   >>> }   
   >>   
   >> Have you thought about a case where the values of check, start,   
   >> and end are chosen from the interval -9000000000 to 9000000000?   
   >> How about the interval -18000000000 to 18000000000?   
   >   
   > Nope, I assume that start and end are between zero and range, and   
   > that check is greater that zero.   
      
   This assumption doesn't match the problem statement (emphasis   
   added):   
      
       Consider >> any << ordered measure that "wraps round"   
      
   What's being asked for is a function that will work with any   
   ordered measure (that wraps), not just some such measures.  An   
   example of such a measure is longitude, which goes from -180   
   to +180 (with one of the two extreme values omitted).  Similarly   
   there is no reason not to allow a measure that is only positive   
   integers but does not include zero.  An important part of the   
   challenge is to come up with a solution that handles these cases   
   as well as the more obvious ones.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)