Question

有没有办法在Haskell中序列化（读/显示）函数？

例如，鉴于：

:t (+1) 
(+1) :: Num a => a -> a

我希望能够有类似的东西：

read "(+1)" :: Num a => a -> a

不幸的是，这会引发错误：

Could not deduce (Read (a -> a)) arising from a use of `read'
from the context (Num a)
  bound by an expression type signature: Num a => a -> a
  at <interactive>:1:1-30
Possible fix:
  add (Read (a -> a)) to the context of
    an expression type signature: Num a => a -> a
  or add an instance declaration for (Read (a -> a))
In the expression: read "(+1)" :: Num a => a -> a
In an equation for `it': it = read "(+1)" :: Num a => a -> a

Answer 1

（通常）不可能显示函数，但如果在运行时有Haskell编译器，原则上可以读取一个函数。

Answer 2

您可以使用plugins包之类的东西在运行时读取代码。正如奥古斯特所说，显示是不可能的。

如何使用它的一个例子：

import System.Eval.Haskell

main = do
  mf <- eval "(+1) :: Int -> Int" []
  case mf of
    Just f -> print $ (f :: Int -> Int) 0
    _      -> putStrLn "Couldn't eval for some reason. :("

Haskell中函数的序列化

2 个答案: