January 2014
Intermediate to advanced
352 pages
6h 34m
Japanese
Content preview from JavaScriptで学ぶ関数型プログラミング
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97
4
章
高階関数
本章は
3
章の内容をさらに一歩すすめる形で、
JavaScript
の関数が第一級の要素で
あることに注目します。
3
章では関数はデータ構造内に存在しデータとして渡すこと
ができるということを説明しました。本章ではこれに加えて、関数は別の関数の戻り
値になることもできるということを説明します。第一級関数の中でも、これらの特徴
をすべて持ちあわせた高階関数（
higher-order function
）についての議論が本章の大
部分を占めます。
高階関数は具体的に以下のように定義されています。
●
第一級データ型である（「ただの値」であるということです。思い出したい
場合は
2
章の最初に戻ってください。）
●
引数として関数をとる
●
関数を戻り値として返す
これまで本書では、他の関数を引数に取る関数を多数紹介してきました。このよう
な関数が関数型プログラミングを支配していることは明らかなので、この領域をより
深く掘り下げます。
4.1
引数として関数をとる関数
本書をここまで読み進めてきた方は、すでに多くの他の関数を引数に取る関数を目
にしていますが、一番顕著にその特徴が現れている関数が
_.map
、
_.reduce
、
_.filter
です。これらの関数は、高階関数の定義を満たしています。しかし、関数型プログラ
ミングにおいて関数が別の関数を引数にとることの重要性を肌で感じるには、これ
98
4 章 高階関数
らの関数の使用例を若干数見るだけでは不足です。したがって、まず関数を引数に取
る関数についてもう少し説明を追加し、その後にクロージャについての説明を行いま ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.