Haskell QuickCheck2使用ByteString？

问题描述

 实例Arbitrary B.ByteString其中
任意= fmap B.pack任意
 coarbitrary =任意。 B.unpack 
  

但是我的GHC 7.2与QuickCheck 2.4.1.1告诉我：

 `coarbitrary'不是'Arbitrary'类的（可见）方法
  

任何指针？

解决方案

coarbitrary 已经转移到QC 2.0中它自己的类型类型 CoAbritary 中，所以只需删除 coarbitrary 的等式。

另见。

The RWH books says that to get ByteString support, I need to add:

instance Arbitrary B.ByteString where
    arbitrary   = fmap B.pack arbitrary
    coarbitrary = coarbitrary . B.unpack

But my GHC 7.2 with QuickCheck 2.4.1.1 tells me:

`coarbitrary' is not a (visible) method of class `Arbitrary'

Any pointers?

解决方案

coarbitrary has moved to it's own typeclass CoAbritary in QC 2.0, so simply just remove the equation for coarbitrary.

Also see the latest documentation.

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