Talk:Convex hull: Difference between revisions
Ok, that IS a bug.
(Raku wrong too) |
Thundergnat (talk | contribs) (Ok, that IS a bug.) |
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::: That said, I also do not know how to isolate a problem which I do not have. --[[User:Rdm|Rdm]] ([[User talk:Rdm|talk]]) 18:59, 24 December 2020 (UTC)
:::: I had the same problem with my Phix translation of the C code, however I <u>only</u> needed to add the fogotten t.
:::: I also added more tests and a simple plot for visual verification of the results. I will also point out that the Raku (and therefore also Sidef) output is wrong in that the (1,-9) of (-3, -9) (1, -9) (14, -9) is clearly colinear and therefore should not be part of the hull. --[[User:Petelomax|Pete Lomax]] ([[User talk:Petelomax|talk]]) 19:19, 24 December 2020 (UTC)
::::: I don't know, if your question is "which of these given points are on the hull?" than then the Raku implementation would be correct. I note that the task is somewhat vague in that regard. At any rate, if it offends you so, change the line <code>if ccw( |@h.tail(2), $point ) >= 0 {</code> to <code>if ccw( |@h.tail(2), $point ) > 0 {</code> and intermediate colinear points will not be reported. It doesn't bother me enough to change it. --[[User:Thundergnat|Thundergnat]] ([[User talk:Thundergnat|talk]]) 22:33, 29 December 2020 (UTC)
:::::: Apparently that's not legal Raku (I put the one = back in and it's fine again, took that one char out and it broke again, a real ??!!??WTF??!! moment):
::::::: Ah, of course: it starts with ((-3, -9), (1, -9)) but the first thing it does is pop the (1,-9). --[[User:Petelomax|Pete Lomax]] ([[User talk:Petelomax|talk]]) 03:21, 30 December 2020 (UTC)
Convex Hull (7 points): [(-3, -9) (19, -8) (17, 5) (12, 17) (5, 19) (-3, 15) (-9, -3)]
Too few positionals passed; expected 3 arguments but got 2
in sub ccw at ./main.raku line 7
in sub graham-scan at ./main.raku line 39
in block <unit> at ./main.raku line 57
exit status 1
:::::: The diagram at 1:00 of the Youtube link is very clear on this matter, plus what he says at 1:22, it seems common sense to me that if the set is every pixel used to draw a 400x400 square outline, the convex hull is 4 points, not all 1,596. --[[User:Petelomax|Pete Lomax]] ([[User talk:Petelomax|talk]]) 03:03, 30 December 2020 (UTC)
:::::::Ah. Ok, '''that''' definitely ''is'' a bug, untrapped edge condition. I'll fix that. While I'm at it, I'll edit the example to ignore colinear points. I don't think my interpretation was completely bogus, but you've convinced me that it is '''less''' correct. (And it's changing one character, not a big deal.) --[[User:Thundergnat|Thundergnat]] ([[User talk:Thundergnat|talk]]) 14:54, 30 December 2020 (UTC)
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