Refactoring Solution - Intro to Computer Science Udacity English Japanese

Refactoring Solution - Intro to Computer ScienceYouTube↗ IA↗(long shot)
Education 2.1K views 8 likes 0 dislikes 23 Feb 2015

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In lecture, Dave pointed out that these 2 functions,

コースの中でデイヴはこの2つの関数hashtable＿updateと hashtable＿lookupが

hashtable_update and hashtable_lookup,

ある似た機能性があり

use some similar functionality that instead we could place in a separate procedure.

さらにこの似た部分を別の関数に入れることもできると指摘しました

Looking at the hashtable_update and lookup procedures here,

hashtable＿updateと hashtable＿lookupの関数を見ると

we see code that's identical between them, namely these 2 lines.

この2行のコードがまったく同じだと確認できます

In both functions, these 2 lines of code go through a given bucket searching for an entry whose first value is the key.

この2行のコードは両関数において 1つ目の値がキーであるエントリを検索するためにバケットを1つ1つ探します

And so what we're going to do is we're going to take this code

行うことはこのコードを用いて

and move it into a separate helper function.

別のヘルパー関数に移動させることです

This is known as refactoring.

これはリファクタリングです

Refactoring is a common software engineering practice

リファクタリングはソフトウエアエンジニアリング共通の慣行で

where we change the code without changing the functionality.

機能性を変えずにコード変更します

There's a number of reasons to do so.

そうする理由がたくさんあります

For example, here we're doing it to minimize duplicated code.

例えば重複したコードを最小化するために行います

This is desirable, because if we want to change how these 2 lines of code work--

これは望ましいですなぜならコードの2行を機能させるために

perhaps we change the structure of the bucket--

バケットの構造を変更するかもしれないからです

we don't want to look through every hash table function

これがどう機能するのか検索しアップデートすれば

searching for how this works and updating them.

すべてのハッシュ関数を調べる必要もありません

Rather, we just want to update it in 1 place.

むしろ1つの場所でアップデートするだけでいいのです

This minimizes bugs and saves time. So let's give it a try.

これによってバグを最小限にして時間を節約できます　試してみましょう

Here I've created a new function called bucket_find.

bucket＿findという新しい関数を作成しました

You should see that it's very similar to the code that we have in update and lookup

これがupdateやlookupのコードとよく似ているのが分かるはずです

in that we're going to go through the bucket searching for the entry

エントリの検索のためバケットを調べていきます

whose first value is the key and then returning the entire entry

その1つ目の値はキーで全体のエントリを渡します

so that we can use it accordingly in both update and lookup.

そうすることでupdateとlookupの両方を使用できます

So now that we have the helper function, let's change our hash table functions to use it.

次はヘルパー関数ですがまずハッシュテーブル関数を変更してみましょう

The resulting code is going to be both simpler and shorter.

最終的なコードはシンプルかつ短いものになります

I've changed hashtable_update.

hashtable＿updateを変更しました

We find the bucket in the first line,

1つ目の行でバケットを見つけられます

then within the bucket we're searching for the key,

そしてバケット内でキーを検索します

and if we find that entry we're going to update the value.

そのエントリが見つけられたら値をアップデートします

Otherwise we're going to append the key and the value to the end of the bucket.

もしくはキーと値をバケットの末尾にappendします

It looks quite a bit simpler than the original function.

元の関数よりかなりシンプルになったように見えます

Let's do the same thing to lookup.

lookupにも同じことを行ってみましょう

In the new hashtable_lookup, we first find the bucket

新しいhashtable＿lookupでまずバケットを見つけ

and then within the bucket we search for the entry.

バケット内でエントリを検索します

If the entry is not None, we return the second value.

エントリがNoneでなければ2つ目の値を返します

Otherwise we return None.

NoneであればNoneを返します

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