Scala - Currying 和默认参数 [英] Scala - Currying and default arguments
问题描述
我有一个带有两个参数列表的函数,我正在尝试部分应用并与 currying 一起使用.第二个参数列表包含所有具有默认值(但不是隐式)的参数.像这样:
I have a function with two parameter lists that I am trying to partially apply and use with currying. The second parameter list contains arguments that all have default values (but not implicit). Something like this:
def test(a: Int)(b: Int = 2, c: Int = 3) { println(a + ", " + b + ", " + c); }
现在,以下一切正常:
test(1)(2, 3);
test(1)(2);
test(1)(c=3);
test(1)();
现在如果我定义:
def partial = test(1) _;
然后可以进行以下操作:
Then the following can be done:
partial(2, 3);
有人可以解释为什么我不能在部分"中省略某些/所有参数,如下所示:
Can someone explain why I can't omit some/all arguments in 'partial' as follows:
partial(2);
partial(c=3);
partial();
写部分"的行为不应该与test(1)"的行为基本相同吗?有人可以帮我找出实现这一目标的方法吗?
Shouldn't writing "partial" behave essentially the same way as "test(1)"? Can someone please help me figure out a way to achieve this?
请帮忙,我很绝望!
编辑 - 由于我无法在 24 小时内回答我自己的问题,我将在此处发布我自己的答案:
EDIT - Since I can't answer my own question within 24 hours, I'll post my own answer here:
这是迄今为止我自己能做到的最好的:
This is the best I could do myself so far:
class Test2(val a: Int) {
def apply(b: Int = 2, c: Int = 3) { println(a + ", " + b + ", " + c); }
}
def test2(a: Int) = new Test2(a);
def partial2 = test2(1); // Note no underscore
test2(1)(2, 3);
test2(1)(2);
test2(1)(c=3);
test2(1)();
partial2(2, 3)
partial2(2);
partial2(c=3);
partial2();
这样就可以了...
推荐答案
这是我目前能做的最好的事情:
This is the best I could do myself so far:
class Test2(val a: Int) {
def apply(b: Int = 2, c: Int = 3) { println(a + ", " + b + ", " + c); }
}
def test2(a: Int) = new Test2(a);
def partial2 = test2(1); // Note no underscore
test2(1)(2, 3);
test2(1)(2);
test2(1)(c=3);
test2(1)();
partial2(2, 3)
partial2(2);
partial2(c=3);
partial2();
这样就可以了...
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