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Circles of given radius through two points: Difference between revisions
Circles of given radius through two points (view source)
Revision as of 03:12, 16 November 2014
, 9 years agoAdd Haskell - Circles of given radius through two points
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=={{header|Haskell}}==
<lang Haskell>add (a, b) (x, y) = (a + x, b + y)
sub (a, b) (x, y) = (a - x, b - y)
magSqr (a, b) = (a ^^ 2) + (b ^^ 2)
mag a = sqrt $ magSqr a
mul (a, b) c = (a * c, b * c)
div2 (a, b) c = (a / c, b / c)
perp (a, b) = (negate b, a)
norm a = a `div2` mag a
circlePoints :: (Ord a, Floating a) =>
(a, a) -> (a, a) -> a -> Maybe ((a, a), (a, a))
circlePoints p q radius
| radius == 0 = Nothing
| p == q = Nothing
| diameter < magPQ = Nothing
| otherwise = Just (center1, center2)
where
diameter = radius * 2
pq = p `sub` q
magPQ = mag pq
midpoint = (p `add` q) `div2` 2
halfPQ = magPQ / 2
magMidC = sqrt . abs $ (radius ^^ 2) - (halfPQ ^^ 2)
midC = (norm $ perp pq) `mul` magMidC
center1 = midpoint `add` midC
center2 = midpoint `sub` midC
uncurry3 f (a, b, c) = f a b c
main :: IO ()
main = mapM_ (print . uncurry3 circlePoints)
[((0.1234, 0.9876), (0.8765, 0.2345), 2),
((0 , 2 ), (0 , 0 ), 1),
((0.1234, 0.9876), (0.1234, 0.9876), 2),
((0.1234, 0.9876), (0.8765, 0.2345), 0.5),
((0.1234, 0.9876), (0.1234, 0.1234), 0)]</lang>
{{out}}
<pre>Just ((-0.8632118016581896,-0.7521118016581892),(1.8631118016581893,1.974211801658189))
Just ((0.0,1.0),(0.0,1.0))
Nothing
Nothing
Nothing</pre>
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