带有Gloss lib的Haskell代码无法编译

Question

我从C++切换到Haskell并使用Gloss来制作游戏.我在main.hs中写了这个有效的代码:

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,我的Gloss lib似乎也缺少一些功能.例如,这个代码,来自gloss-examples包的"Game Event",编译和运行完美(非常漂亮):

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.错误表明:

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

扫描Gloss的文档,它看起来像你正在寻找

rectangleWire :: Float -> Float -> PictureSource

以原点为中心的线框矩形,具有给定的宽度和高度.出口自Graphics.Gloss.Data.Picture.