November 2017
Beginner to intermediate
344 pages
7h 2m
Chinese
Content preview from 深入理解運算原理｜從簡單的機器到無所不能的程式
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第8章
不可能的程式
我認為，世界上最仁慈的事情是人類的心智無法將其所有內容相互聯繫。
—
H.P.
洛奎夫
（
H. P. Lovecraft
）
我們在本書探討了不同類型的電腦和程式設計語言，包括幾種抽象機。這些機器當中有
一些的能力比其他機器更為強大，尤其有兩種更是具有明顯的限制：有限自動機無法
解決無限制計數的相關問題，例如要決定一串括號是否對稱；而下推自動機則無法處理
任何需要在多處重複使用資訊的問題，例如要決定字串是否包含相同數量的
a
、
b
、
c
字
元。
但是我們看見最先進的設備，也就是圖靈機，似乎擁有我們需要的一切：它可以任何
順序、任意的循環、條件式、副常式來存取沒有限制的儲存空間。第 6 章極小的程式
語言，也就是 lambda 演算，也獲得證明具有驚人的能力：利用一些創造力，它允許我
們將簡單的值和複雜的資料結構表示成純粹的程式碼，並且也能實作操縱這些表示的運
算。而在第 7 章，我們看到了許多其他簡單的系統，例如 lambda 演算，都具有和圖靈
機一樣的通用能力。
這種日益強大的系統，我們還能往前推動到什麼地步？也許並非模糊不清：我們藉著增
加沒有進展的功能，而試著讓圖靈機更具運算能力，這樣的作法可能會對運算能力造成
嚴重的限制。那麼，電腦和程式語言的基本能力究竟為何，有什麼是它們做不到的嗎？
有任何不可能的程式嗎？
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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.