公司网站建设解决方案,详情页制作,linux网站服务器配置,memcache wordpress好的计算机编程语言应具备的三个特性
基础单元表达式#xff0c;计算机编程语言最最最基础单元#xff0c;理应具备的表达式组合的能力#xff0c;能够通过基础单元表达式组合成更复杂的元素抽象的能力#xff0c;能通过复杂的元素抽象成更高层的单元
基础单元表达式 加 …好的计算机编程语言应具备的三个特性
基础单元表达式计算机编程语言最最最基础单元理应具备的表达式组合的能力能够通过基础单元表达式组合成更复杂的元素抽象的能力能通过复杂的元素抽象成更高层的单元
基础单元表达式 加 减 乘 除。 其实加 减 乘 除才是最牛逼的接口左边和右边提供输入参数最后返回计算结果又是最基础的可以组合成更复杂单元的基础单元表达式接口。 SICP javascript版本可以在网页版解释运行环境中写代码
在线快乐地编写javascript代码并运行
137 349;
4861000 - 334;
6665 * 99;
49510 / 4;
2.52.7 10;
12.73 * 2 * (3 - 5 4) 27 / 6 * 10; Naming and the Environment
const pi 3.14159;
const radius 10;pi * radius * radius;
314.159const circumference 2 * pi * radius;
circumference;
62.8318Evaluating Operator Combinations One of our goals in this chapter is to isolate issues about thinking procedurally. (2 4 * 6) * (3 12); In general, we shall see that recursion is a very powerful technique for dealing with hierarchical, treelike objects.
Compound Functions
Numbers and arithmetic operations are primitive data and functions.Nesting of combinations provides a means of combining operations.Constant declarations that associate names with values provide a limited means of abstraction.
function square(x)
{return x*x;
}square(21);square(2 5);function square(x)
{return x*x;
}square(21);square(2 5);square(square(3));// x² y² can be expressed as
// square(x) square(y)function sum_of_squares(x,y)
{return square(x) square(y);
}sum_of_squares(3,4);
25// now we can use sum_of_squares as a building block in constructing further functions.
function f(a)
{return sum_of_squares(a 1,a * 2);
}f(5);
136
上述计算模型 square及sum_of_squares都可以是外部领域模型所以一个大型系统可以由很多外部领域模型组合成复杂功能。 突然间恍然大悟上面这个计算机中的精灵图EVAL计算出规则APPLY的结果计算得到的结果又再次成为规则APPLY的输入然后EVAL又再次计算得到规则APPLY的结果
Conditional Expressions and Predicates function abs(x)
{return x 0 ? x : -x;
}abs(3);abs(-43);function greater_or_equal(x,y)
{return x y || x y;
}greater_or_equal(3,4);greater_or_equal(4,4);greater_or_equal(6,2);function greater_or_equal(x,y)
{return !( x y);
}
练习题
10;5 3 4;9 - 1;6 / 2;2 * 4 (4 - 6);const a 3;
const b a 1;a b a * b;a b;b a b a * b ? b : a;a 4 ? 6 : b 4 ? 6 7 a : 25;
exercise 1.1 exercise 1.2 exercise 1.3
(5 4 (2 - (3 - (6 4 / 5)))) / (3 * (6 - 2) * (2 - 7));function square(x)
{return x * x;
}function square_of_the_larger_two(x,y,z)
{return x y ? (y z ? (square(x) square(y)) : (square(x) square(z))) :(x z ? (square(x) square(y)) : (square(y) square(z)));
}square_of_the_larger_two(2,3,4);square_of_the_larger_two(2,1,3);
