Re: Advent of code day 12

[John Perry <john.perry@usm.edu>]

On Sunday, December 13, 2020 at 3:14:30 AM UTC-6, gautier...@hotmail.com wrote:
> > I mostly agree, but I had trouble with today's puzzle. It's a recurring problem of mine: if the input is not specified completely, I have trouble figuring out what it is, even when I study it, so I often get subtle bugs. And there's a LOT of input. In my input, a turn of 270 degrees doesn't show up until line 85, so I didn't see it even after scanning the file (which I did because I wanted to make sure it had integer-only positions and the turns were multiples of 90). Once I figured that out, it was quite easy.
> If you include all possible angles you don't encounter that issue :-) 
> 
> https://github.com/zertovitch/hac/blob/master/exm/aoc/2020/aoc_2020_12.adb

Yes, I had looked at your code (and Max's) after finishing mine but before replying here, so I was aware of it at the time. That is definitely one way to avoid the issue :-) but I don't think you can use the approach I used in that case, of which I am perhaps far too fond:

   Left_Turn: array( Direction_Value, Direction_Delta ) of Direction_Value :=
   (
          ( West,  South, East  ),   -- 90, 180, 270 from north
          ( East,  North, West  ),   -- ...from south
          ( North, West,  South ),   -- ...from east
          ( South, East,  North )    -- ...from west
   );
   
so the code to perform a left turn is

   Direction := Left_Turn(Direction, D);

john perry