Game.LambdaHack.Common.Point

Basic operations on 2D points represented as linear offsets.

Documentation

data Point

2D points in cartesian representation. Coordinates grow to the right and down, so that the (0, 0) point is in the top-left corner of the screen. Coordinates are never negative (unlike for Vector) and the X coordinate never reaches the screen width as read from speedupHackXSize.

Constructors

Point

Fields

• px :: X
• py :: Y

Instances

Enum Point

Defined in Game.LambdaHack.Common.Point

Methods

succ :: Point -> Point

pred :: Point -> Point

toEnum :: Int -> Point

fromEnum :: Point -> Int

enumFrom :: Point -> [Point]

enumFromThen :: Point -> Point -> [Point]

enumFromTo :: Point -> Point -> [Point]

enumFromThenTo :: Point -> Point -> Point -> [Point]

Eq Point

Defined in Game.LambdaHack.Common.Point

Methods

(==) :: Point -> Point -> Bool

(/=) :: Point -> Point -> Bool

Ord Point

Defined in Game.LambdaHack.Common.Point

Methods

compare :: Point -> Point -> Ordering

(<) :: Point -> Point -> Bool

(<=) :: Point -> Point -> Bool

(>) :: Point -> Point -> Bool

(>=) :: Point -> Point -> Bool

max :: Point -> Point -> Point

min :: Point -> Point -> Point

Show Point

Defined in Game.LambdaHack.Common.Point

Methods

showsPrec :: Int -> Point -> ShowS

show :: Point -> String

showList :: [Point] -> ShowS

Generic Point

Defined in Game.LambdaHack.Common.Point

Associated Types

type Rep Point :: Type -> Type

Methods

from :: Point -> Rep Point x

to :: Rep Point x -> Point

Arbitrary Point

Defined in Game.LambdaHack.Common.Point

Methods

arbitrary :: Gen Point

shrink :: Point -> [Point]

Binary Point

Defined in Game.LambdaHack.Common.Point

Methods

put :: Point -> Put

get :: Get Point

putList :: [Point] -> Put

type Rep Point

Defined in Game.LambdaHack.Common.Point

type Rep Point = D1 ('MetaData "Point" "Game.LambdaHack.Common.Point" "LambdaHack-0.11.0.0-inplace" 'False) (C1 ('MetaCons "Point" 'PrefixI 'True) (S1 ('MetaSel ('Just "px") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 X) :*: S1 ('MetaSel ('Just "py") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedStrict) (Rec0 Y)))

type PointI = Int

Enumeration representation of Point.

chessDist :: Point -> Point -> Int

The distance between two points in the chessboard metric.

>>> chessDist (Point 0 0) (Point 0 0)
0
>>> chessDist (Point (-1) 0) (Point 0 0)
1
>>> chessDist (Point (-1) 0) (Point (-1) 1)
1
>>> chessDist (Point (-1) 0) (Point 0 1)
1
>>> chessDist (Point (-1) 0) (Point 1 1)
2

chessDist p1 p2 >= 0

chessDist p1 p2 ^ (2 :: Int) <= euclidDistSq p1 p2

euclidDistSq :: Point -> Point -> Int

Squared euclidean distance between two points.

adjacent :: Point -> Point -> Bool

Checks whether two points are adjacent on the map (horizontally, vertically or diagonally).

bresenhamsLineAlgorithm :: Int -> Point -> Point -> Maybe [Point]

Bresenham's line algorithm generalized to arbitrary starting eps (eps value of 0 gives the standard BLA). Skips the source point and goes through the second point to infinity. Gives Nothing if the points are equal. The target is given as Point, not PointI, to permit aiming out of the level, e.g., to get uniform distributions of directions for explosions close to the edge of the level.

>>> bresenhamsLineAlgorithm 0 (Point 0 0) (Point 0 0)
Nothing
>>> take 3 $ fromJust $ bresenhamsLineAlgorithm 0 (Point 0 0) (Point 1 0)
[(1,0),(2,0),(3,0)]
>>> take 3 $ fromJust $ bresenhamsLineAlgorithm 0 (Point 0 0) (Point 0 1)
[(0,1),(0,2),(0,3)]
>>> take 3 $ fromJust $ bresenhamsLineAlgorithm 0 (Point 0 0) (Point 1 1)
[(1,1),(2,2),(3,3)]

fromTo :: Point -> Point -> [Point]

A list of all points on a straight vertical or straight horizontal line between two points. Fails if no such line exists.

>>> fromTo (Point 0 0) (Point 2 0)
[(0,0),(1,0),(2,0)]

originPoint :: Point

insideP :: (X, Y, X, Y) -> Point -> Bool

Checks that a point belongs to an area.

speedupHackXSize :: PrimArray X

This is a hack to pass the X size of the dungeon, defined in game content, to the Enum instances of Point and Vector. This is already slower and has higher allocation than hardcoding the value, so passing the value explicitly to a generalization of the Enum conversions is out of the question. Perhaps this can be done cleanly and efficiently at link-time via Backpack, but it's probably not supported yet by GHCJS (not verified). For now, we need to be careful never to modify this array, except for setting it at program start before it's used for the first time. Which is easy, because Point is never mentioned in content definitions. The PrimArray has much smaller overhead than IORef and reading from it looks cleaner, hence its use.

Internal operations

bresenhamsLineAlgorithmBegin :: Int -> Point -> Point -> [Point]

Bresenham's line algorithm generalized to arbitrary starting eps (eps value of 0 gives the standard BLA). Includes the source point and goes through the target point to infinity.

>>> take 4 $ bresenhamsLineAlgorithmBegin 0 (Point 0 0) (Point 2 0)
[(0,0),(1,0),(2,0),(3,0)]

balancedWord :: Int -> Int -> Int -> [Int]

See http://roguebasin.roguelikedevelopment.org/index.php/index.php?title=Digital_lines.