Data.CG.Minus.Bearing

Compass bearings.

Documentation

data Bearing

Enumeration of compass bearings

Constructors

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

Instances

Bounded Bearing

Enum Bearing

Eq Bearing

Show Bearing

bearing :: Pt R -> Pt R -> Bearing

Bearing from Pt p to q.

 let f (x,y) = bearing (Pt 0 0) (Pt x y)
 map f [(0,1),(1,1),(1,0),(1,-1)] == [N,NE,E,SE]
 map f [(0,-1),(-1,-1),(-1,0),(-1,1)] == [S,SW,W,NW]
 map f [(1/4,1),(1,1/4),(1,-1/4),(1/4,-1)] == [NNE,ENE,ESE,SSE]
 map f [(-1/4,-1),(-1,-1/4),(-1,1.4),(-1/4,1)] == [SSW,WSW,NW,NNW]

bearing_8 :: Pt R -> Pt R -> Bearing

Bearing to nearest eight point compass bearing

 let f (x,y) = bearing_8 (Pt 0 0) (Pt x y)
 map f [(1/4,1),(1,1/4),(1,-1/4),(1/4,-1)] == [N,E,E,S]

bearing_opposite :: (Bearing, Bearing) -> Bool

Predicate that is True if bearings are opposite.

 bearing_opposite (NW,SE) == True
 map bearing_opposite (zip [N,E,S,W] [S,W,N,E]) == [True,True,True,True]