Question

想要打印0到10之间的随机数，但生成似乎未定义无法编译，下面的代码从例子中编辑我正在使用Haskell Platform 2011.2.0.1

更新：

import System.IO
import System.Random
import Test.QuickCheck.Function
import Test.QuickCheck.Gen
import Test.QuickCheck

main :: IO() 
main = putStrLn (show result)
  where result = unGen (choose (0, 10)) (mkStdGen 1) 1

产生的错误：

test6.hs:13:25:
    Ambiguous type variable `a0' in the constraints:
      (Random a0) arising from a use of `choose' at test6.hs:13:25-30
      (Show a0) arising from a use of `show' at test6.hs:12:18-21
      (Num a0) arising from the literal `10' at test6.hs:13:36-37
    Probable fix: add a type signature that fixes these type variable(s)
    In the first argument of `unGen', namely `(choose (0, 10))'
    In the expression: unGen (choose (0, 10)) (mkStdGen 1) 1
    In an equation for `result':
        result = unGen (choose (0, 10)) (mkStdGen 1) 1

Answer 1

好的，第一个问题是让我们创建一个本地绑定，并且你在全局范围内使用它，如果你想让绑定对主操作是本地的，我会用到哪里进行绑定。查看QuickCheck文档，似乎不再存在generate函数。 unGen具有相同的类型签名，所以我相信它已取代它。

import System.Random
import Test.QuickCheck
import Test.QuickCheck.Gen

main :: IO ()
main = putStrLn (show result)
  where result = unGen (choose (0::Int, 10::Int)) (mkStdGen 1) 1

函数在Haskell Platform 2011.2.0.1中生成的位置

1 个答案: