Name: Java 教程 - 瞭解部分應用 (Java Tutorial - Understanding partial application)
Uploaded: 2022-11-04T17:45:38.000Z
Duration: 8 min 24 s

- [Shaun] So what is partial application?

partial application is when we take a function

部分應用是指當我們把一個函數

and we fix some of those arguments to a set value.

而我們把其中一些參數固定為一個設定值。

can then be called from anywhere else in the code,

然後可以從代碼中的其他地方調用。

and it'll be as if we had called the original function

Another way to think about it as like this:

通常情況下，當我們調用一個函數時。

we have to pass all the arguments into it

What partial application allows us to do,

once the function gets all of the arguments it needs.

一旦函數得到它所需要的所有參數。

Now, partial application is also a very useful way

現在，部分應用也是一個非常有用的方法

if there's a function that we use often in our code,

如果有一個我們在代碼中經常使用的函數。

where one or more of the arguments that we call it with

其中的一個或多個參數，我們用它來調用

So now that we know what partial application is,

是以，現在我們知道什麼是部分應用。

它在代碼中到底是什麼樣子的？

Well, let's imagine that we have a simple add function,

好吧，讓我們想象一下，我們有一個簡單的添加函數。

And it's going to take three integers as arguments.

and it's going to return an integer as well.

所以，現在我們有了這個函數。

what if we wanted to fix one of these arguments

如果我們想修正其中的一個論點呢？

so that we only had to pass in the other two arguments

這樣，我們只需要傳入另外兩個參數

and this function will take a single integer as an argument,

而這個函數將接受一個單一的整數作為參數。

And we have to import both the BiFunction

and it's going to return another function

And finally, once it has all of those three arguments,

最後，一旦它擁有了所有這三個論據。

it's going to call add dot apply, with x, y, and z.

它將調用add dot apply，其中包括x、y和z。

So now that we have this addPartial function,

所以現在我們有了這個addPartial函數。

We're going to say BiFunction, integer, integer, integer,

我們要說的是BiFunction, integer, integer, integer。

add five equals addPartial dot apply five.

So now the first argument x has been fixed to five,

所以現在第一個參數x已經被固定為5。

通過調用add partial dot apply five。

And what we can do now is we can call this add five function

而我們現在可以做的是，我們可以調用這個添加5的函數

所以你可以看到它是什麼樣子的。

所以我們可以說增加五個點的應用。

and we can call it with the remaining two arguments,

我們可以用剩下的兩個參數來調用它。

we'll see that it prints out the correct result.

我們將看到它打印出了正確的結果。

except we passed in the five and the six and seven

除了我們在五號、六號和七號中通過之外

So in this example that we just went through,

是以，在我們剛剛經歷的這個例子中。

we can divide up our arguments however we want.

我們可以隨心所欲地劃分我們的論點。

we could pass in the first two arguments,

and it would take two arguments and return a function,

並且它將接受兩個參數並返回一個函數。

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Java 教程 - 瞭解部分應用 (Java Tutorial - Understanding partial application)

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