[英]How to compose curried functions in Scala
Is it possible compose functions in Scala that are curried?是否可以在 Scala 中组合柯里化函数? For example:
例如:
def a(s1: String)(s2: String): Int = s1.length + s2.length
def b(n: Int): Boolean = n % 2 == 0
def x : String => String => Boolean = a andThen b
x("blabla")("foo")
Edit :编辑 :
I've found a way of doing it in Haskell :我在 Haskell 中找到了一种方法:
a :: String -> String -> Int
a s1 s2 = length s1 + length s2
b :: Int -> Bool
b n = mod n 2 == 0
c :: String -> String -> Bool
c = curry (b . (uncurry a))
This should work:这应该有效:
def x = a _ andThen (_ andThen b)
The first _
avoids invoking a
and makes it into a function value.第一个
_
避免调用a
并将其变成函数值。 This value is of type String=>String=>Int
, ie a function that takes String
and returns String=>Int
.该值的类型为
String=>String=>Int
,即一个接受String
并返回String=>Int
的函数。
The argument to the andThen
method is a function that takes the result of the original function and modifies it. andThen
方法的参数是一个函数,它接受原始函数的结果并对其进行修改。 So in this case it requires a function that takes String=>Int
and returns a new value, a function String=>Boolean
.所以在这种情况下,它需要一个接受
String=>Int
并返回一个新值的函数,一个函数String=>Boolean
。 We can fabricate this new function by using andThen
on the original function.我们可以通过在原始函数上使用
andThen
来andThen
这个新函数。 This takes the result of a
and composes it with the new function b
.这需要的结果,
a
和新功能组成它b
。
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