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如何引用作用域中两个函数具有相同名称的特定函数

scala

0

Yaneeve · 技术社区 · 7 年前

假设在作用域中有两个函数具有相同的名称,但参数列表不同。如何区分两者,例如在尝试访问 tupled

scala> :paste
// Entering paste mode (ctrl-D to finish)


def f(s: String, l: Long): String = ???
def f(i: Int, l: Long): String = ???

val t:((String, Long)) => String = f.tupled

// Exiting paste mode, now interpreting.

<pastie>:15: error: ambiguous reference to overloaded definition,
both method f of type (i: Int, l: Long)String
and  method f of type (s: String, l: Long)String
match expected type ?
val t:((String, Long)) => String = f.tupled

将问题简化为函数文字会产生:

scala> :paste
// Entering paste mode (ctrl-D to finish)

def f(i: Int, l: Long): String = ???
def f(s: String, l: Long): String = ???

val g = f _

// Exiting paste mode, now interpreting.

<pastie>:15: error: ambiguous reference to overloaded definition,
both method f of type (s: String, l: Long)String
and  method f of type (i: Int, l: Long)String
match expected type ?
val g = f _
        ^

apply 方法不起作用

scala>

scala> :paste
// Entering paste mode (ctrl-D to finish)

def f(s: String, l: Long): String = ???
def f(i: Int, l: Long): String = ???

val g: (String, Long) => String  = f _

// Exiting paste mode, now interpreting.

f: (s: String, l: Long)String <and> (i: Int, l: Long)String
f: (s: String, l: Long)String <and> (i: Int, l: Long)String
g: (String, Long) => String = $$Lambda$1458/794413935@60cbba57

2 回复 | 直到 7 年前

1

3

dyrkin 7 年前

以下是实现这一目标的方法

val t1 = (f(_: String, _: Long)).tupled
val t2 = (f(_: Int, _: Long)).tupled

t1: ((String, Long)) => String = scala.Function2$$Lambda$1188/922196321@3994b698
t2: ((Int, Long)) => String = scala.Function2$$Lambda$1188/922196321@4249db51

2

0

Yaneeve 7 年前

我发现了下面的黑客 tupled 问题:

scala> :paste
// Entering paste mode (ctrl-D to finish)

def f(s: String, l: Long): String = ???
def f(i: Int, l: Long): String = ???

val g: (String, Long) => String  = f _
val t = g.tupled

// Exiting paste mode, now interpreting.

f: (s: String, l: Long)String <and> (i: Int, l: Long)String
f: (s: String, l: Long)String <and> (i: Int, l: Long)String
g: (String, Long) => String = $$Lambda$1476/1981627424@172f2717
t: ((String, Long)) => String = scala.Function2$$Lambda$259/530042637@bda4cbe