Haskell提供
typed holes.
例：
f :: Int -> String -> Bool f x y = if (x > 10) then True else (g y) g :: String -> Bool g s = _
汇编：
Prelude> :l HoleEx.hs
[1 of 1] Compiling Main ( HoleEx.hs,interpreted )
HoleEx.hs:6:7:
Found hole `_' with type: Bool
Relevant bindings include
s :: String (bound at HoleEx.hs:6:3)
g :: String -> Bool (bound at HoleEx.hs:6:1)
In the expression: _
In an equation for `g': g s = _
Failed,modules loaded: none.
在Scala中编程时,我通常使用???作为我的Scala代码中的占位符,我还没写过.
但是,使用打字孔对我来说似乎更强大.请注意,我可以用else替换上面的其他(g y)(g 55),但是我得到一个编译时错误：
Prelude> :l HoleEx.hs
[1 of 1] Compiling Main ( HoleEx.hs,interpreted )
HoleEx.hs:3:39:
Couldn't match type `Int' with `[Char]'
Expected type: String
Actual type: Int
In the first argument of `g',namely `x'
In the expression: (g x)
Failed,modules loaded: none.
虽然我可以使用???在Scala中获取占位符实现进行编译,与孔不同,我将使用???获取运行时错误.
scala> def g(x: Int): Int = ??? g: (x: Int)Int scala> g(5) scala.NotImplementedError: an implementation is missing
Scala是否有打孔？
