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PO"Couldn't match expected type" error
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copied!<p>Here is my code:</p> <pre><code>xandy :: Element_w_Coord Cell -> Coord xandy (e, (x, y)) = (x, y) transition_world :: Ordered_Lists_2D Cell -> Element_w_Coord Cell -> Ordered_Lists_2D Cell transition_world world (cell, (x, y)) = case (cell, (x, y)) of (Head, (x, y))-> map_Ordered_Lists_2D Tail world (Tail, (x, y)) -> map_Ordered_Lists_2D Conductor world (Empty, (x, y)) -> map_Ordered_Lists_2D Empty world (Conductor, (x, y)) -> map_Ordered_Lists_2D Head world </code></pre> <p>And here is the error message:</p> <pre><code>Sources/Transitions/For_Ordered_Lists_2D.hs:33:43: Couldn't match expected type `Element_w_Coord e0 -> Cell' with actual type `Cell' In the first argument of `map_Ordered_Lists_2D', namely `Tail' In the expression: map_Ordered_Lists_2D Tail world In a case alternative: (Head, (x, y)) -> map_Ordered_Lists_2D Tail world </code></pre> <p>Anyone likes to tell me what's wrong with my code pls?</p> <p>Btw, here is the definition for </p> <pre><code>type Ordered_Lists_2D e = [Sparse_Line e] data Sparse_Line e = Sparse_Line {y_pos :: Y_Coord, entries :: Placed_Elements e} data Placed_Element e = Placed_Element {x_pos :: X_Coord, entry :: e} type Placed_Elements e = [Placed_Element e] map_Ordered_Lists_2D :: (Element_w_Coord e -> b) -> Ordered_Lists_2D e -> Ordered_Lists_2D b map_Ordered_Lists_2D f world = case world of l: ls -> map_line f l: map_Ordered_Lists_2D f ls [] -> [] where map_line :: (Element_w_Coord e -> b) -> Sparse_Line e -> Sparse_Line b map_line f line = Sparse_Line {y_pos = (y_pos line), entries = map_elements f (y_pos line) (entries line)} where map_elements :: (Element_w_Coord e -> b) -> Y_Coord -> Placed_Elements e -> Placed_Elements b map_elements f y elements = case elements of c: cs -> Placed_Element {x_pos = (x_pos c), entry = f ((entry c), ((x_pos c), y))}: map_elements f y cs [] -> [] </code></pre> <p>Thanks for anyone who can good me some advice XD</p>

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