45 lines
1.0 KiB
Haskell
45 lines
1.0 KiB
Haskell
module Geometry.LHS
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( isLHS
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, isRHS
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) where
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import Geometry.Data
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import Geometry.Vector
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-- | Test whether a point is on the LHS of a line.
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-- Returns False if the line is of zero length.
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isLHS
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:: Point2 -- ^ First line point.
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-> Point2 -- ^ Second line point.
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-> Point2 -- ^ Point not on line.
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-> Bool
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{-# INLINE isLHS #-}
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isLHS
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(V2 x y)
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(V2 x' y')
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(V2 x'' y'')
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| (x,y) == (x',y') = False
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| otherwise = a1 * b2 - a2 * b1 > 0
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where
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a1 = x' - x
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a2 = y' - y
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b1 = x'' - x
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b2 = y'' - y
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-- | Test whether a point is on the LHS of a line.
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-- Returns False if the line is of zero length.
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isRHS
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:: Point2 -- ^ First line point.
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-> Point2 -- ^ Second line point.
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-> Point2 -- ^ Point not on line.
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-> Bool
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{-# INLINE isRHS #-}
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isRHS
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(V2 x y)
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(V2 x' y')
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(V2 x'' y'')
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| (x,y) == (x',y') = False
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| otherwise = a1 * b2 - a2 * b1 < 0
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where
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a1 = x' - x
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a2 = y' - y
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b1 = x'' - x
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b2 = y'' - y
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