Scala：（Int，Int）=> Int 不匹配 (Int, Int) => INT
我正在尝试使用 y-combinator 在 scala 中定义 gcd：
object Main {
def y[A,B]( f : (A => B) => A => B ) : A => B = f(y(f))
def gcd = y[(Int,Int),Int]( (g) => (x,y) => if (x == 0) y else g(y % x, x) )
}
但我收到一个错误：
Main.scala:3: error: type mismatch;
found : (Int, Int) => Int
required: (Int, Int) => Int
def gcd = y[(Int,Int),Int]( (g) => (x :Int,y :Int) => if (x == 0) y else g(y % x, x) )
^
如果我柯里化所有参数，那么就没有问题：
def gcd = y[Int,Int => Int]( g => x => y => if (x == 0) y else g(y % x)(x) )
我在未柯里化版本中做错了什么？
I'm trying to use the y-combinator to define gcd in scala:
object Main {
def y[A,B]( f : (A => B) => A => B ) : A => B = f(y(f))
def gcd = y[(Int,Int),Int]( (g) => (x,y) => if (x == 0) y else g(y % x, x) )
}
But I'm getting an error:
Main.scala:3: error: type mismatch;
found : (Int, Int) => Int
required: (Int, Int) => Int
def gcd = y[(Int,Int),Int]( (g) => (x :Int,y :Int) => if (x == 0) y else g(y % x, x) )
^
If I curry all the arguments, then there's no problem:
def gcd = y[Int,Int => Int]( g => x => y => if (x == 0) y else g(y % x)(x) )
What am I doing wrong in the uncurried version?
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带有
(g) => 的位（x：Int，y：Int）=>。 Scala 期望您的参数是 (Int,Int) 的元组，因此它更像(g) =>; (tup: (Int, Int)) =>您可以使用一些模式匹配来避免在 tup 上使用
_1和_2匹配。这对我来说编译得很好：The bit with
(g) => (x :Int,y :Int) =>. Scala expects your argument to be a tuple of (Int,Int), so it would be more like(g) => (tup: (Int, Int)) =>You can use a bit of pattern matching to avoid having to use
_1and_2matching on tup. This compiles just fine for me: