haskell - 具有Gloss lib的Haskell代码无法编译

Question

我从C++切换到Haskell，并使用Gloss制作游戏。
我在main.hs中编写了此有效代码:

import Graphics.Gloss.Interface.Pure.Game

events (EventKey (Char 'a') Down _ _) _ = RectangleWire 10 10
events _ x = x

main = play (InWindow "GameEvent" (700, 100) (10, 10))
    white
    100
    (Circle 10.0)
    id
    events
    (\_ world -> world)

然后命令ghc main.hs回答:

[1 of 1] Compiling Main             ( main.hs, main.o )

main.hs:3:43: Not in scope: data constructor `RectangleWire'

即使我安装了最新版本，Gloss库中似乎也缺少一些功能。例如，以下代码来自“gloss-examples”包中的“游戏事件”，可以完美地编译并运行(如此漂亮):

import Graphics.Gloss

-- | Display the last event received as text.
main
 = play (InWindow "GameEvent" (700, 100) (10, 10))
        white
        100
        ""
        (\str     -> Translate (-340) 0 $ Scale 0.1 0.1 $ Text str)
        (\event _ -> show event)
        (\_ world -> world)

Answer 1

您的代码无法编译，因为您引用的数据构造函数RectangleWire不在范围内。该错误表明:

main.hs:3:43: Not in scope: data constructor `RectangleWire'

扫描documentation for Gloss，好像您在寻找

rectangleWire :: Float -> Float -> PictureSource

具有给定宽度和高度的以原点为中心的线框矩形。从Graphics.Gloss.Data.Picture导出。