Haskell. How to fix scope issue?

Drovosek012018-05-25 04:33:55

Haskell

Drovosek01, 2018-05-25 04:33:55

I'm trying to load a module in ghci, but it gives errors

C:\Users\Egor\Documents\HaskellCoursework\Second.hs:85:5: error: 
Variable not in scope: 
applyViewPortToPicture 
:: Graphics.Gloss.Data.ViewPort.ViewPort -> Picture -> Picture 
| 
85 | applyViewPortToPicture port $ 
| ^^^^^^^^^^^^^^^^^^^^^^ 

C:\Users\Egor\Documents\HaskellCoursework\Second.hs:89:61: error: 
Variable not in scope: graphEdges :: Graph -> Set Edge 
| 
89 | edges = Pictures [drawEdge e sc | e <- Set.toList (graphEdges gr)] 
| ^^^^^^^^^^ 

C:\Users\Egor\Documents\HaskellCoursework\Second.hs:99:40: error: 
* Variable not in scope: normaliseV :: Point -> Vector 
* Perhaps you meant `normalizeV' (imported from Graphics.Gloss.Data.Vector) 
| 
99 | if l > 0 then (charge / l) `mulSV` normaliseV d else 0 
| ^^^^^^^^^^ 

C:\Users\Egor\Documents\HaskellCoursework\Second.hs:154:22: error: 
Variable not in scope: 
invertViewPort 
:: Graphics.Gloss.Data.ViewPort.ViewPort -> (Float, Float) -> Point 
| 
154 | case findVertex (invertViewPort port pos) (viewPortScale port) sc of 
| ^^^^^^^^^^^^^^ 

C:\Users\Egor\Documents\HaskellCoursework\Second.hs:154:48: error: 
Variable not in scope: 
viewPortScale :: Graphics.Gloss.Data.ViewPort.ViewPort -> Float 
| 
154 | case findVertex (invertViewPort port pos) (viewPortScale port) sc of 
| ^^^^^^^^^^^^^ 

C:\Users\Egor\Documents\HaskellCoursework\Second.hs:165:33: error: 
Variable not in scope: 
invertViewPort 
:: Graphics.Gloss.Data.ViewPort.ViewPort -> (Float, Float) -> Point 
| 
165 | sc{scPoints = Map.insert v (invertViewPort port pos) pts} 
| ^^^^^^^^^^^^^^ 
Failed, no modules loaded. 
Prelude>

Here is the module code:

import Data.Map.Strict (Map)
import qualified Data.Map.Strict as Map
import Data.Set (Set)
import qualified Data.Set as Set
import System.Random

import Graphics.Gloss
import Graphics.Gloss.Data.Vector
import Graphics.Gloss.Data.ViewState
import Graphics.Gloss.Interface.Pure.Game

type Vertex = Int
type Edge = (Vertex, Vertex)
-- INVARIANT Every `Vertex` present in a set of neighbours is
-- present as a key in the `Map`.
newtype Graph = Graph {grNeighs :: Map Vertex (Set Vertex)}

emptyGraph :: Graph
emptyGraph = Graph Map.empty

addVertex :: Vertex -> Graph -> Graph
addVertex v (Graph neighs) =
    Graph $ case Map.lookup v neighs of
                Nothing -> Map.insert v Set.empty neighs
                Just _  -> neighs

addEdge :: Edge -> Graph -> Graph
addEdge (v1, v2) gr = Graph neighs
  where
    gr'    = addVertex v1 (addVertex v2 gr)
    neighs = Map.insert v1 (Set.insert v2 (vertexNeighs v1 gr')) $
             Map.insert v2 (Set.insert v1 (vertexNeighs v2 gr')) $
             grNeighs gr'

vertexNeighs :: Vertex -> Graph -> Set Vertex
vertexNeighs v (Graph neighs) = neighs Map.! v

-- INVARIANT The keys in `scGraph` are the same as the keys
-- in `scPoints`.
data Scene =
    Scene { scGraph     :: Graph
          , scPoints    :: Map Vertex Point
          , scSelected  :: Maybe Vertex
          , scViewState :: ViewState }

emptyScene :: Scene
emptyScene =
    Scene{ scGraph     = emptyGraph
         , scPoints    = Map.empty
         , scSelected  = Nothing
         , scViewState = viewStateInit }

scAddVertex :: Vertex -> Point -> Scene -> Scene
scAddVertex v pt [email protected]Scene{scGraph = gr, scPoints = pts} =
    sc{scGraph = addVertex v gr, scPoints = Map.insert v pt pts}

scAddEdge :: Edge -> Scene -> Scene
scAddEdge [email protected](v1, v2) [email protected]Scene{scGraph = gr, scPoints = pts} =
    if Map.member v1 pts && Map.member v2 pts
    then sc{scGraph = addEdge e gr}
    else error "scAddEdge: non existant point!"

vertexPos :: Vertex -> Scene -> Point
vertexPos v Scene{scPoints = pts} = pts Map.! v

vertexRadius :: Float
vertexRadius = 6

vertexColor :: Color
vertexColor = makeColor 1 0 0 1 -- Red

edgeColor :: Color
edgeColor = makeColor 1 1 1 0.8 -- Whiteish

drawVertex :: Vertex -> Scene -> Picture
drawVertex v sc =
    Translate x y (ThickCircle (vertexRadius / 2) vertexRadius)
  where (x, y) = vertexPos v sc

drawEdge :: Edge -> Scene -> Picture
drawEdge (v1, v2) sc = Line [vertexPos v1 sc, vertexPos v2 sc]

drawScene :: Scene -> Picture
drawScene [email protected]Scene{scGraph = gr, scViewState = ViewState{viewStateViewPort = port}} =
    applyViewPortToPicture port $
    Pictures [Color edgeColor edges, Color vertexColor vertices]
  where
    vertices = Pictures [drawVertex n sc | n <- Map.keys (grNeighs gr)    ]
    edges    = Pictures [drawEdge e sc   | e <- Set.toList (graphEdges gr)]

charge :: Float
charge = 100000

pushForce :: Point         -- Vertex we're calculating the force for
          -> Point         -- Vertex pushing the other away
          -> Vector
pushForce v1 v2 =
    -- If we are analysing the same vertex, l = 0
    if l > 0 then (charge / l) `mulSV` normaliseV d else 0
  where
    d = v1 - v2
    l = magV d ** 2

stiffness :: Float
stiffness = 1 / 2

pullForce :: Point -> Point -> Vector
pullForce v1 v2 = stiffness `mulSV` (v2 - v1)

updatePosition :: Float       -- Time since the last update
               -> Vertex      -- Vertex we are analysing
               -> Scene
               -> Point       -- New position
updatePosition dt v1 [email protected]Scene{scPoints = pts, scGraph = gr} =
    v1pos + pull + push
  where
    v1pos  = vertexPos v1 sc

    -- Gets a velocity by multiplying the time by the force (we take
    -- the mass to be 1).
    getVel f v2pos = dt `mulSV` f v1pos v2pos

    -- Sum all the pushing and pulling.  All the other vertices push,
    -- the connected vertices pull.
    push = Map.foldr' (\v2pos -> (getVel pushForce v2pos +)) 0 pts
    pull = foldr (\v2pos -> (getVel pullForce v2pos +)) 0
                 [vertexPos v2 sc | v2 <- Set.toList (vertexNeighs v1 gr)]

updatePositions :: Float -> Scene -> Scene
updatePositions dt [email protected]Scene{scSelected = sel, scGraph = Graph neighs} =
    foldr f sc (Map.keys neighs)
  where
    f n sc' =
        let pt = if Just n == sel
                 then vertexPos n sc else updatePosition dt n sc'
        in scAddVertex n pt sc'

inCircle :: Point             -- Where the user has clicked
         -> Float             -- The scaling factor in the ViewPort
         -> Point             -- The position of the vertex
         -> Bool
inCircle p sca v = magV (v - p) <= vertexRadius * sca

findVertex :: Point -> Float -> Scene -> Maybe Vertex
findVertex p1 sca Scene{scPoints = pts} =
    Map.foldrWithKey' f Nothing pts
  where
    f _ _  (Just v) = Just v
    f v p2 Nothing  = if inCircle p1 sca p2 then Just v else Nothing

handleEvent :: Event -> Scene -> Scene

handleEvent (EventKey (MouseButton LeftButton) Down Modifiers{ctrl = Down} pos) sc =
    case findVertex (invertViewPort port pos) (viewPortScale port) sc of
        Nothing -> sc
        Just v  -> sc{scSelected = Just v}
  where
    viewState = scViewState sc
    port      = viewStateViewPort viewState

handleEvent (EventKey (MouseButton LeftButton) Up _ _) [email protected]Scene{scSelected = Just _} =
    sc{scSelected = Nothing}

handleEvent (EventMotion pos) [email protected]Scene{scPoints = pts, scSelected = Just v} =
    sc{scPoints = Map.insert v (invertViewPort port pos) pts}
 where
   port = viewStateViewPort (scViewState sc)

handleEvent ev sc =
    sc{scViewState = updateViewStateWithEvent ev (scViewState sc)}

-- Taken from <http://www.graphviz.org/Gallery/undirected/transparency.gv.txt>.
sampleGraph :: [Edge]
sampleGraph =
    [(1,  30), (1,  40), (8,  46), (8,  16), (10, 25), (10, 19), (10, 33),
     (12, 8 ), (12, 36), (12, 17), (13, 38), (13, 24), (24, 49), (24, 13),
     (24, 47), (24, 12), (25, 27), (25, 12), (27, 12), (27, 14), (29, 10),
     (29, 8 ), (30, 24), (30, 44), (38, 29), (38, 35), (2,  42), (2,  35),
     (2,  11), (14, 18), (14, 24), (14, 38), (18, 49), (18, 47), (26, 41),
     (26, 42), (31, 39), (31, 47), (31, 25), (37, 26), (37, 16), (39, 50),
     (39, 14), (39, 18), (39, 47), (41, 31), (41, 8 ), (42, 44), (42, 29),
     (44, 37), (44, 32), (3,  20), (3,  28), (6,  45), (6,  28), (9,  6 ),
     (9,  16), (15, 16), (15, 48), (16, 50), (16, 32), (16, 39), (20, 33),
     (33, 9 ), (33, 46), (33, 48), (45, 15), (4,  17), (4,  15), (4,  12),
     (17, 21), (19, 35), (19, 15), (19, 43), (21, 19), (21, 50), (23, 36),
     (34, 23), (34, 24), (35, 34), (35, 16), (35, 18), (36, 46), (5,  7 ),
     (5,  36), (7,  32), (7,  11), (7,  14), (11, 40), (11, 50), (22, 46),
     (28, 43), (28, 8 ), (32, 28), (32, 39), (32, 42), (40, 22), (40, 47),
     (43, 11), (43, 17)
    ]

windowSize :: (Int, Int)
windowSize = (640, 480)

fromEdges :: StdGen -> [Edge] -> Scene
fromEdges gen es =
    foldr scAddEdge (fst (Set.foldr' addv (emptyScene, gen) vs)) es
  where
    vs = Set.fromList (concat [[v1, v2] | (v1, v2) <- es])

    halfWidth  = fromIntegral (fst windowSize) / 2
    halfHeight = fromIntegral (snd windowSize) / 2

    addv v (sc, gen1) =
        let (x, gen2) = randomR (-halfWidth,  halfWidth ) gen1
            (y, gen3) = randomR (-halfHeight, halfHeight) gen2
        in  (scAddVertex v (x, y) sc, gen3)

sceneWindow :: Scene -> IO ()
sceneWindow sc =
    play (InWindow "Graph Drawing - ctrl + left mouse button to drag" windowSize (10, 10))
         black 30 sc drawScene handleEvent updatePositions

main :: IO ()
main =
    do gen <- getStdGen
       sceneWindow (fromEdges gen sampleGraph)

Judging by an error of a problem with area of visibility. I tried adjusting the spaces, but that didn't make a difference.
Copy-pasted and linked the code from here: https://mazzo.li/posts/graph-drawing.html
Please help me solve the problem.

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[[+comments_count]] answer(s)

Drovosek01, 2018-05-25
@Drovosek01

They helped fix it here: www.cyberforum.ru/haskell/thread2252789.html#post1...
Here is the working code, if someone needs it:

{-# LANGUAGE FlexibleInstances #-}

import Data.Map.Strict (Map)
import qualified Data.Map.Strict as Map
import Data.Set (Set)
import qualified Data.Set as Set
import System.Random
 
import Graphics.Gloss
import Graphics.Gloss.Data.Vector
import Graphics.Gloss.Data.ViewState
import Graphics.Gloss.Interface.Pure.Game
import Graphics.Gloss.Data.ViewPort

instance Num (Float, Float) where
  (xl,yl) + (xr,yr) = (xl+xr,yl+yr)
  (xl,yl) - (xr,yr) = (xl-xr,yl-yr)
  (xl,yl) * (xr,yr) = undefined
  fromInteger n = (fromInteger n,0)
  abs (x,y) = undefined
  signum (x,y) = undefined

type Vertex = Int
type Edge = (Vertex, Vertex)
-- INVARIANT Every `Vertex` present in a set of neighbours is
-- present as a key in the `Map`.
newtype Graph = Graph {grNeighs :: Map Vertex (Set Vertex)}
 
emptyGraph :: Graph
emptyGraph = Graph Map.empty
 
addVertex :: Vertex -> Graph -> Graph
addVertex v (Graph neighs) =
    Graph $ case Map.lookup v neighs of
                Nothing -> Map.insert v Set.empty neighs
                Just _  -> neighs
 
addEdge :: Edge -> Graph -> Graph
addEdge (v1, v2) gr = Graph neighs
  where
    gr'    = addVertex v1 (addVertex v2 gr)
    neighs = Map.insert v1 (Set.insert v2 (vertexNeighs v1 gr')) $
             Map.insert v2 (Set.insert v1 (vertexNeighs v2 gr')) $
             grNeighs gr'
 
vertexNeighs :: Vertex -> Graph -> Set Vertex
vertexNeighs v (Graph neighs) = neighs Map.! v

graphEdges :: Graph -> Set Edge
graphEdges = Map.foldrWithKey' foldNeighs Set.empty . grNeighs
  where
    -- For each vertex `v1`, insert an edge for each neighbour `v2`.
    foldNeighs v1 ns es =
         Set.foldr' (\v2 -> Set.insert (order (v1, v2))) es ns
    order (v1, v2) = if v1 > v2 then (v1, v2) else (v2, v1)
-- INVARIANT The keys in `scGraph` are the same as the keys
-- in `scPoints`.
data Scene =
    Scene { scGraph     :: Graph
          , scPoints    :: Map Vertex Point
          , scSelected  :: Maybe Vertex
          , scViewState :: ViewState }
 
emptyScene :: Scene
emptyScene =
    Scene{ scGraph     = emptyGraph
         , scPoints    = Map.empty
         , scSelected  = Nothing
         , scViewState = viewStateInit }
 
scAddVertex :: Vertex -> Point -> Scene -> Scene
scAddVertex v pt [email protected]Scene{scGraph = gr, scPoints = pts} =
    sc{scGraph = addVertex v gr, scPoints = Map.insert v pt pts}
 
scAddEdge :: Edge -> Scene -> Scene
scAddEdge [email protected](v1, v2) [email protected]Scene{scGraph = gr, scPoints = pts} =
    if Map.member v1 pts && Map.member v2 pts
    then sc{scGraph = addEdge e gr}
    else error "scAddEdge: non existant point!"
 
vertexPos :: Vertex -> Scene -> Point
vertexPos v Scene{scPoints = pts} = pts Map.! v
 
vertexRadius :: Float
vertexRadius = 6
 
vertexColor :: Color
vertexColor = makeColor 1 0 0 1 -- Red
 
edgeColor :: Color
edgeColor = makeColor 1 1 1 0.8 -- Whiteish
 
drawVertex :: Vertex -> Scene -> Picture
drawVertex v sc =
    Translate x y (ThickCircle (vertexRadius / 2) vertexRadius)
  where (x, y) = vertexPos v sc
 
drawEdge :: Edge -> Scene -> Picture
drawEdge (v1, v2) sc = Line [vertexPos v1 sc, vertexPos v2 sc]
 
drawScene :: Scene -> Picture
drawScene [email protected]Scene{scGraph = gr, scViewState = ViewState{viewStateViewPort = port}} =
    applyViewPortToPicture port $
    Pictures [Color edgeColor edges, Color vertexColor vertices]
  where
    vertices = Pictures [drawVertex n sc | n <- Map.keys (grNeighs gr)    ]
    edges    = Pictures [drawEdge e sc   | e <- Set.toList (graphEdges gr)]
 
charge :: Float
charge = 100000
 
pushForce :: Point         -- Vertex we're calculating the force for
          -> Point         -- Vertex pushing the other away
          -> Vector
pushForce v1 v2 =
    -- If we are analysing the same vertex, l = 0
    if l > 0 then (charge / l) `mulSV` normalizeV d else 0
  where
    d = v1 - v2
    l = magV d ** 2
 
stiffness :: Float
stiffness = 1 / 2
 
pullForce :: Point -> Point -> Vector
pullForce v1 v2 = stiffness `mulSV` (v2 - v1)
 
updatePosition :: Float       -- Time since the last update
               -> Vertex      -- Vertex we are analysing
               -> Scene
               -> Point       -- New position
updatePosition dt v1 [email protected]Scene{scPoints = pts, scGraph = gr} =
    v1pos + pull + push
  where
    v1pos  = vertexPos v1 sc
 
    -- Gets a velocity by multiplying the time by the force (we take
    -- the mass to be 1).
    getVel f v2pos = dt `mulSV` f v1pos v2pos
 
    -- Sum all the pushing and pulling.  All the other vertices push,
    -- the connected vertices pull.
    push = Map.foldr' (\v2pos -> (getVel pushForce v2pos +)) 0 pts
    pull = foldr (\v2pos -> (getVel pullForce v2pos +)) 0
                 [vertexPos v2 sc | v2 <- Set.toList (vertexNeighs v1 gr)]
 
updatePositions :: Float -> Scene -> Scene
updatePositions dt [email protected]Scene{scSelected = sel, scGraph = Graph neighs} =
    foldr f sc (Map.keys neighs)
  where
    f n sc' =
        let pt = if Just n == sel
                 then vertexPos n sc else updatePosition dt n sc'
        in scAddVertex n pt sc'
 
inCircle :: Point             -- Where the user has clicked
         -> Float             -- The scaling factor in the ViewPort
         -> Point             -- The position of the vertex
         -> Bool
inCircle p sca v = magV (v - p) <= vertexRadius * sca
 
findVertex :: Point -> Float -> Scene -> Maybe Vertex
findVertex p1 sca Scene{scPoints = pts} =
    Map.foldrWithKey' f Nothing pts
  where
    f _ _  (Just v) = Just v
    f v p2 Nothing  = if inCircle p1 sca p2 then Just v else Nothing
 
handleEvent :: Event -> Scene -> Scene
 
handleEvent (EventKey (MouseButton LeftButton) Down Modifiers{ctrl = Down} pos) sc =
    case findVertex (invertViewPort port pos) (viewPortScale port) sc of
        Nothing -> sc
        Just v  -> sc{scSelected = Just v}
  where
    viewState = scViewState sc
    port      = viewStateViewPort viewState
 
handleEvent (EventKey (MouseButton LeftButton) Up _ _) [email protected]Scene{scSelected = Just _} =
    sc{scSelected = Nothing}
 
handleEvent (EventMotion pos) [email protected]Scene{scPoints = pts, scSelected = Just v} =
    sc{scPoints = Map.insert v (invertViewPort port pos) pts}
 where
   port = viewStateViewPort (scViewState sc)
 
handleEvent ev sc =
    sc{scViewState = updateViewStateWithEvent ev (scViewState sc)}
 
-- Taken from <http://www.graphviz.org/Gallery/undirected/transparency.gv.txt>.
sampleGraph :: [Edge]
sampleGraph =
    [(1,  30), (1,  40), (8,  46), (8,  16), (10, 25), (10, 19), (10, 33),
     (12, 8 ), (12, 36), (12, 17), (13, 38), (13, 24), (24, 49), (24, 13),
     (24, 47), (24, 12), (25, 27), (25, 12), (27, 12), (27, 14), (29, 10),
     (29, 8 ), (30, 24), (30, 44), (38, 29), (38, 35), (2,  42), (2,  35),
     (2,  11), (14, 18), (14, 24), (14, 38), (18, 49), (18, 47), (26, 41),
     (26, 42), (31, 39), (31, 47), (31, 25), (37, 26), (37, 16), (39, 50),
     (39, 14), (39, 18), (39, 47), (41, 31), (41, 8 ), (42, 44), (42, 29),
     (44, 37), (44, 32), (3,  20), (3,  28), (6,  45), (6,  28), (9,  6 ),
     (9,  16), (15, 16), (15, 48), (16, 50), (16, 32), (16, 39), (20, 33),
     (33, 9 ), (33, 46), (33, 48), (45, 15), (4,  17), (4,  15), (4,  12),
     (17, 21), (19, 35), (19, 15), (19, 43), (21, 19), (21, 50), (23, 36),
     (34, 23), (34, 24), (35, 34), (35, 16), (35, 18), (36, 46), (5,  7 ),
     (5,  36), (7,  32), (7,  11), (7,  14), (11, 40), (11, 50), (22, 46),
     (28, 43), (28, 8 ), (32, 28), (32, 39), (32, 42), (40, 22), (40, 47),
     (43, 11), (43, 17)
    ]
 
windowSize :: (Int, Int)
windowSize = (640, 480)
 
fromEdges :: StdGen -> [Edge] -> Scene
fromEdges gen es =
    foldr scAddEdge (fst (Set.foldr' addv (emptyScene, gen) vs)) es
  where
    vs = Set.fromList (concat [[v1, v2] | (v1, v2) <- es])
 
    halfWidth  = fromIntegral (fst windowSize) / 2
    halfHeight = fromIntegral (snd windowSize) / 2
 
    addv v (sc, gen1) =
        let (x, gen2) = randomR (-halfWidth,  halfWidth ) gen1
            (y, gen3) = randomR (-halfHeight, halfHeight) gen2
        in  (scAddVertex v (x, y) sc, gen3)
 
sceneWindow :: Scene -> IO ()
sceneWindow sc =
    play (InWindow "Graph Drawing - ctrl + left mouse button to drag" windowSize (10, 10))
         black 30 sc drawScene handleEvent updatePositions
 
main :: IO ()
main =
    do gen <- getStdGen
       sceneWindow (fromEdges gen sampleGraph)