我目前正在开发一个 haskell 程序，该程序从文本框中获取用户输入，然后使用System.Plugins库编译和加载它，以便提取图片以绘制到屏幕上。用户可以在文本框中编辑代码，然后通过单击编译按钮重新加载他们的新图像。这是单击编译按钮时触发的代码：
compileText :: SourceView -> SOE.Window -> IO ()
compileText tview w = do
txtBuff <- textViewGetBuffer tview
startIt <- textBufferGetStartIter txtBuff
endIt <- textBufferGetEndIter txtBuff
compTime <- getClockTime
srcString <- textBufferGetByteString txtBuff startIt endIt False
BS.writeFile "Test.hs" srcString
mkStat <- make "Test.hs" []
case mkStat of
MakeSuccess cd fp -> print fp
MakeFailure (er1:er2:errs) -> error er2
loadResult <- getModule
case loadResult of
Right (md, pic) -> do
runGraphics $ do
draw3 "gtk test" pic w
unload md
Left errors -> print errors
return ()
getModule :: IO (Either [String] (Module, Picture))
getModule = do
mv <- load "Test.o" ["."] [] "pic"
case mv of
LoadFailure messages -> return (Left messages)
LoadSuccess x y -> return (Right (x, y))
这是用户在文本框中输入的一些示例代码：
module Test where
import Picture
r1,r2,r3,r4 :: Region
r1 = Shape(Rectangle 2 1)
r2 = Shape(Ellipse 2 1.5)
r3 = Shape(RtTriangle 3 2)
r4 = Shape(Polygon [(-2.5, 2.5), (-3.0,0), (-1.7,-1.0), (-1.1,0.2),(-1.5,2.0)])
p1,p2,p3,p4 :: Picture
p1 = Region Red r1
p2 = Region Green r2
p3 = Region Blue r3
p4 = Region Yellow r4
pics :: Picture
pics = foldl Over EmptyPic [p1,p2,p3,p4]
如果用户编写的代码每次都能正确编译和加载，这一切都按预期工作。但是，当用户编写一段无法加载的代码时（我一直在玩的示例是将 'pic' 更改为 'pics'，因此它无法找到要加载的 pic 函数）预期的行为是程序将打印加载错误到屏幕，以便用户可能更正他们的代码并尝试再次单击编译按钮。
然而，实际发生的情况是，一旦程序遇到一次 LoadFailure，所有后续点击编译按钮的尝试都会导致加载失败消息，无论代码是否正确！
我不太确定这里到底发生了什么，但似乎该程序保留了从评估到评估的先前结果的一些记忆。如何获得我正在寻找的行为？
编辑：我试图通过编写一个小测试用例来隔离问题，该用例说明了我在不使用 gtk 的情况下遇到的问题
import Control.Monad
import System.Time
import System.IO
import qualified Data.ByteString as BS
import qualified Data.ByteString.Char8 as BSC
import System.Plugins.Make
import System.Plugins.Load
import System.Eval.Haskell
testCaseCorrect :: String
testCaseCorrect = "module Test where\n printGreeting :: String -> IO ()\n printGreeting greeting = print greeting"
-- This should cause load to fail as it will not be able to find the
-- printGreeting function
testCaseIncorrect :: String
testCaseIncorrect = "module Test where\n printGurting :: String -> IO ()\n printGurting greeting = print greeting"
main :: IO ()
main = do
BS.writeFile "Test.hs" (BSC.pack testCaseCorrect)
mkStat <- make "Test.hs" []
case mkStat of
MakeSuccess cd fp -> print fp
MakeFailure (er1:er2:errs) -> error er2
loadResult <- getModule
case loadResult of
Right (md, greeter) -> do
greeter "Hi there"
unload md
Left errors -> print errors
BS.writeFile "Test.hs" (BSC.pack testCaseIncorrect)
mkStat2 <- make "Test.hs" []
case mkStat2 of
MakeSuccess cd fp -> print fp
MakeFailure (er1:er2:errs) -> error er2
loadResult2 <- getModule
case loadResult2 of
Right (md, greeter) -> do
greeter "Hi there"
unload md
Left errors -> print errors
BS.writeFile "Test.hs" (BSC.pack testCaseCorrect)
mkStat3 <- make "Test.hs" []
case mkStat3 of
MakeSuccess cd fp -> print fp
MakeFailure (er1:er2:errs) -> error er2
loadResult3 <- getModule
case loadResult3 of
Right (md, greeter) -> do
greeter "Hi there"
unload md
Left errors -> print errors
getModule :: IO (Either [String] (Module, String -> IO()))
getModule = do
mv <- load "Test.o" ["."] [] "printGreeting"
case mv of
LoadFailure messages -> return (Left messages)
LoadSuccess x y -> return (Right (x, y))
此代码产生结果：
"Test.o"
"Hi there"
"Test.o"
["load: couldn't find symbol <<printGreeting>>"]
"Test.o"
["load: couldn't find symbol <<printGreeting>>"]
即它设法复制错误
编辑2：似乎在一些完全相同的代码运行它也会产生输出：
"Test.o"
"Hi there"
"Test.o"
"Hi there"
"Test.o"
"Hi there"
但我认为这可能是由于连续编译一起运行得如此之快。