But just what is an object? At its simplest, an object has two components: Internal state. This is embodied by variables known only to the object. A variable only visible within the object is called a private variable. As a consequence, it is impossible – if the object decides so – to know the internal state of the object from another object. A repertoire of behaviors. These are the messages an object instance responds to. When the object receives a message it understands, it gets its behavior from a method with that name known by its class or superclass.

学习编译原理有什么好的书籍?

（sicp 计算机程序的构造和解释） 如何理解无限长的流？

如何看待编程语言越来越大的趋势？

计算机系大四学生如何在六个月的时间内完成一个编译器？要学些什么？

学习 scheme 有哪些资源推荐？

有什么项目适合用racket实现？最近看完SICP要练练手．

Racket这种可以把语言特性写成库的语言为何没有得到广泛的工业应用？

什么是卫生宏, 跟普通的宏以及函数有什么区别?

函数式语言能否内置一个 caching 类似的功能用于函数 Memoization, 为什么?

Racket里的Macro都可以用来做些什么？

Essentials of Programming Languages 第五章 trampolined interpreter不知道如何实现？

手撸解释器教程《Crafting Interpreters》中文翻译

EOPL是一本怎样的书？和SICP如何比较？

如何看待Berkeley开设的CS61A:SICP in Python课程？

如何通俗的理解将语法分析和执行分离的好处？

如何评价SICP？

如何评价 Why MIT stopped teaching SICP？

SICP 和 CSAPP 中的哪些题目让你感到受益匪浅？

SICP 是不是被高估了？

SICP中环境模型可以等价为龙书中(第七章)讲的的运行时刻环境么？

CPS变换可以用来将普通递归转变为尾递归？？

你在南京大学上过最牛的课是什么？

SICP换零钱迭代方法实现，是如何写的？

《计算机程序的构造和解释（SICP）》讨论的核心问题是什么？

读完sicp后应该做些什么？

sicp中的流模式在实际开发中有什么应用？

可以基于意图去使用各种协调分布式系统的工具，而不用深入具体工具的实现细节去研究怎么解决的分布式难题

Applicative order versus normal order According to the description of evaluation given in 1.1.3, the interpreter first evaluates the operator and operands and then applies the resulting procedure to the resulting arguments. This is not the only way to perform evaluation. An alternative evaluation model would not evaluate the operands until their values were needed. Instead it would first substitute operand expressions for parameters until it obtained an expression involving only primitive operators, and would then perform the evaluation.

recursion equations

Thus, programs must be written for people to read, and only incidentally for machines to execute.

Each breakthrough in hardware technology leads to more massive programming enterprises, new organizational principles, and an enrichment of abstract models. Every reader should ask himself periodically “Toward what end, toward what end?”—but do not ask it too often lest you pass up the fun of programming for the constipation of bittersweet philosophy.

The source of the exhilaration associated with computer programming is the continual unfolding within the mind and on the computer of mechanisms expressed as programs and the explosion of perception they generate. If art interprets our dreams, the computer executes them in the guise of programs!