GHCI 无法为“System.Time”加载接口

Question

我正在学习 Haskell 并尝试从书中构建示例。当我在 GHCI 中使用“:l BetterPredicate”命令加载代码时，出现以下错误：

Prelude> :l BetterPredicate
[1 of 2] Compiling RecursiveContents ( RecursiveContents.hs, interpreted )

RecursiveContents.hs:12:32: warning: [-Wtabs]
    Tab character found here.
    Please use spaces instead.
[2 of 2] Compiling Main             ( BetterPredicate.hs, interpreted )

BetterPredicate.hs:3:1: error:
    Failed to load interface for ‘System.Time’
    Perhaps you meant
      System.CPUTime (from base-4.9.1.0)
      System.Cmd (from process-1.4.3.0)
      System.Mem (from base-4.9.1.0)
    Use -v to see a list of the files searched for.
Failed, modules loaded: RecursiveContents.

这是我要编译的代码：

import Control.Monad (filterM)
import System.Directory (Permissions (..), getModificationTime, getPermissions)
import System.Time (ClockTime(..))
import System.FilePath (takeExtension)
import Control.Exception (bracket, handle)
import System.IO (IOMode(..), hClose, hFileSize, openFile)

-- Our functions
import RecursiveContents (getRecursiveContents)

type Predicate = FilePath        -- Path to directory entry
              -> Permissions     -- permissions
              -> Maybe Integer   -- file size (Nothing if not file)
              -> ClockTime       -- last modified
              -> Bool
-- TBD
getFileSize :: FilePath -> IO (Maybe Integer)

betterFind :: Predicate -> FilePath -> IO [FilePath]
betterFind p path = getRecursiveContents >>= filterM check
    where check name = do 
              perms <- getPermissions name
              size  <- getFileSize name
              modified <- getModificationTime name 
              return (p name perms size modified)

simpleFileSize :: FilePath -> IO Integer
simpleFileSize path = do
    h <- openFile path ReadMode
    size <- hFileSize h
    hClose
    return size

saferFileSize :: FilePath -> IO (Maybe Integer)
saferFileSize path = handle (\_ -> return Nothing) $ do
    h <- openFile path ReadMode
    size <- hFileSize h
    hClose
    return (Just size)

getFileSize :: FilePath -> IO (Maybe Integer)
getFileSize path = handle (\_ -> return Nothing) $
    bracket (openFile path ReadOnly) hClose $ \h -> do
        size <- hFileSize h
        hClose
        return (Just size)


type InfoP a =  FilePath       -- path to directory entry
             -> Permissions    -- permissions
             -> Maybe Integer  -- file size (Nothing if not file)
             -> ClockTime      -- last modified
             -> a 

pathP :: InfoP FilePath
pathP path _ _ _ = path

sizeP :: InfoP Integer
sizeP _ _ (Just size) _ = size
sizeP _ _ Nothing     _ = -1

equalP :: (Eq a) => InfoP a -> a -> InfoP Bool
--equalP f k = \w x y z -> f w x y z == k
equalP f k w x y z = f w x y z == k

根据文档：http://hackage.haskell.org/package/old-time-1.1.0.3/docs/System-Time.html 这个模块是旧库的一部分，所以我想我需要以某种方式导入它，但如果我不构建使用 Cabal（没有 *.cabal 文件）或其他东西的包，我只想在 GHCI 中使用我的代码。

Answer 1

只需使用cabal install全局安装一个包

$ cabal install old-time

它会给你一个警告，但如果你只是用它来支持 ghci 也没关系。

另请注意 the documentation 警告：

This library is deprecated, please look at Data.Time in the time package instead.

GHCI 无法为“System.Time”加载接口

GHCI Failed to load interface for ‘System.Time’

haskell

haskell-platform