有没有办法将两组图片合并为一组？

Question

我正在尝试用一组单元格显示线条网格，这些单元格填充所述线条中的方块。

我已经尝试过像简单列表一样连接它们。

这是网格线。它自己正确显示。

grid = translate (fromIntegral width * (-0.5)) 
                 (fromIntegral height * (-0.5)) 
                 (pictures (concat [
                                    [line [(i * unitWidth, 0.0)
                                          ,(i * unitWidth, fromIntegral height)]
                                    ,line [(0.0, i * unitHeight)
                                          ,(fromIntegral width, i * unitHeight)]
                                    ]
                                   | i <- [1..gridDimension]]
                            )
                 )

这是在线条之间绘制的一组单位，它自己也能正确显示。

units = pictures [translate ((x*unitWidth - unitWidth/2) + (fromIntegral width*(-0.5))) 
                            ((y*unitHeight - unitHeight/2) + (fromIntegral height*(-0.5)))
                            unit
                 | x <- [1..gridDimension], y <- [1..gridDimension]]

我的主要方法：

main = display window backgroundColor units

我可以在这个地方用单位换网格，效果很好。我也试过这个：

main = display window backgroundColor (units++grid)

它引发了以下错误：

40: error:
    • Couldn't match expected type ‘[a0]’ with actual type ‘Picture’
    • In the first argument of ‘(++)’, namely ‘grid’
      In the third argument of ‘display’, namely ‘(grid ++ units)’
      In the expression: display window backgroundColor (grid ++ units)
   |
10 | main = display window backgroundColor (grid++units)
   |                                        ^^^^

/home/georg/Desktop/THM/6_semester/funktionale_programmierung/my/app/Main.hs:10:40: error:
    • Couldn't match expected type ‘Picture’ with actual type ‘[a0]’
    • In the third argument of ‘display’, namely ‘(grid ++ units)’
      In the expression: display window backgroundColor (grid ++ units)
      In an equation for ‘main’:
          main = display window backgroundColor (grid ++ units)
   |
10 | main = display window backgroundColor (grid++units)
   |                                        ^^^^^^^^^^^

/home/georg/Desktop/THM/6_semester/funktionale_programmierung/my/app/Main.hs:10:46: error:
    • Couldn't match expected type ‘[a0]’ with actual type ‘Picture’
    • In the second argument of ‘(++)’, namely ‘units’
      In the third argument of ‘display’, namely ‘(grid ++ units)’
      In the expression: display window backgroundColor (grid ++ units)
   |
10 | main = display window backgroundColor (grid++units)
   |                                              ^^^^^

Answer 1

(++) :: [a] -> [a] -> [a]函数附加了两个列表，一个Picture不是列表，所以你不能使用那个函数。

但是您可以在此处使用 (<>) :: Semigroup m => m -> m -> m，因为 Picture 是 Semigroup:

的一个实例

因此我们可以这样写：

main = display window backgroundColor (<b>units <> grid</b>)

或者您可以再次使用 pictures :: [Picture] -> Picture，并包括您的 units 和 grid，例如：

main = display window backgroundColor (<b>pictures [units, grid]</b>)

有没有办法将两组图片合并为一组？

Is there a way to merge two sets of pictures into one?

haskell

gloss