Re: Laws for Show and Read?

5 Jun 2019


      In the instance Show Foo, I mean "showsPrec" rather than "show".

2019년 6월 5일 (수) 16:45, Dannyu NDos 님이 작성:
...
Shouldn't it be laws that "show" must be injective and "read" must be
surjective? Without such laws, one could define:
data Foo = Foo
instance Show Foo where
    show _ _ = id
instance Read Foo where
    readPrec = pfail
which should be prevented.