版本9和11间的区别 (跳过第2版)

Building Abstractions with Procedures

1. Procedures and the Processes They Generate

1.2.1 Linear Recursion and Iteration 1.2.2 Tree Recursion 1.2.3 Orders of Growth 1.2.4 Exponentiation 1.2.5 Greatest Common Divisors 1.2.6 Example: Testing for Primality

1.3 Formulating Abstractions with Higher-Order Procedures
- 1.3.1 Procedures as Arguments 1.3.2 Constructing Procedures Using Lambda 1.3.3 Procedures as General Methods 1.3.4 Procedures as Returned Values

-  ⇤ ← 于2007-04-16 10:20:06修订的的版本9 → 
  大小: 4411
  编辑: czk
  备注:
+   ← 于2007-04-16 10:38:49修订的的版本11 → ⇥
  大小: 637
  编辑: czk
  备注:
-删除的内容标记成这样。
+加入的内容标记成这样。
 行号 3:
-== The Elements of Programming ==
=== Expressions ===
 1. {{{
486
}}}{{{#!python
486
}}}

 1. {{{
(+ 137 349)
486
(- 1000 334)
666
(* 5 99)
495
(/ 10 5)
2
(+ 2.7 10)
12.7
}}}{{{#!python
137 + 349
1000 - 334
5 * 99
10 / 5
2.7 + 10
}}}

 1. {{{
(+ 21 35 12 7)
75

(* 25 4 12)
1200
}}}{{{#!python
21 + 35 + 12 + 7
25 * 4 * 12
}}}或者{{{
reduce(int.__add__, [21, 35, 12, 7])
reduce(int.__mul__, [25, 4, 12])
}}}
 1. {{{
(+ (* 3 5) (- 10 6))
19
}}}{{{#!python
(3 * 5) + (10 - 6)
}}}
 1. {{{
(+ (* 3
      (+ (* 2 4)
         (+ 3 5)))
   (+ (- 10 7)
      6))
}}}{{{#!python
(3 * ((2*4)+(3+5)) ) + ((10-7)+6)
}}}
=== Naming and the Environment ===
 1. {{{
(define size 2)
}}}{{{#!python
size = 2
}}}
 1. {{{
size
2
(* 5 size)
10
}}}{{{#!python
size
5 * size
}}}
 1. {{{
(define pi 3.14159)
(define radius 10)
(* pi (* radius radius))
314.159
(define circumference (* 2 pi radius))
circumference
62.8318
}}}{{{#!python
pi = 3.14159
radius = 10
pi * (radius * radius)
circumference = 2 * pi * radius
circumference
}}}

=== Evaluating Combinations ===
 1. {{{
(* (+ 2 (* 4 6))
   (+ 3 5 7))
}}}{{{#!python
(2+(4*6)) * (3+5+7)
}}}

=== Compound Procedures ===
 1. {{{
(define (square x) (* x x))
}}}{{{#!python
square = lambda x: x*x
}}}
 1. {{{
(square 21)
441

(square (+ 2 5))
49

(square (square 3))
81
}}}{{{#!python
square(21)
square(2+5)
square(square(3))
}}}
 1. {{{
(define (sum-of-squares x y)
  (+ (square x) (square y)))

(sum-of-squares 3 4)
25
}}}{{{#!python
sum_of_squares = lambda x, y: square(x) + square(y)
sum_of_squares(3, 4)
}}}
 1. {{{
(define (f a)
  (sum-of-squares (+ a 1) (* a 2)))

(f 5)
136
}}}{{{#!python
f = lambda a:sum_of_squares(a+1, a*2)
f(5)
}}}
=== The Substitution Model for Procedure Application ===

=== Conditional Expressions and Predicates ===
 1. {{{
(define (abs x)
  (cond ((> x 0) x)
        ((= x 0) 0)
        ((< x 0) (- x))))
}}}{{{#!python
abs = lambda x: x if x > 0 else ( 0 if x == 0 else (-x if x < 0 else 0))
}}}或者{{{#!python
abs = lambda x: x if x > 0 else (0 if x == 0 else -x)
}}}
 1. {{{
(define (abs x)
  (cond ((< x 0) (- x))
        (else x)))
}}} {{{#!python
abs = lambda x: -x if x < 0 else x
}}}
 1. {{{
(define (abs x)
  (if (< x 0)
      (- x)
      x))
}}}{{{
abs = lambda x: -x if x < 0 else x
}}}
 1. {{{
(and (> x 5) (< x 10))
}}}{{{#!python
x > 5 and x < 10
}}}
 1. {{{
(define (>= x y)
  (or (> x y) (= x y)))
}}}{{{#!python
greater_or_equal = lambda x, y: x>y or x==y
}}}
 1. {{{
(define (>= x y)
  (not (< x y)))
}}}{{{#!python
greater_or_equal = lambda x, y: not x < y
}}}

=== Example: Square Roots by Newton's Method ===
 1. {{{
(define (sqrt-iter guess x)
  (if (good-enough? guess x)
      guess
      (sqrt-iter (improve guess x)
                 x)))
}}}{{{#!python
sqrt_iter = lambda guess, x: guess if good_enough(guess, x) else sqrt_iter(improve(guess, x), x)
}}}
 1. {{{
(define (improve guess x)
  (average guess (/ x guess)))
}}}{{{#!python
improve = lambda guess, x: average(guess, x/guess)
}}}
 1. {{{
(define (average x y)
  (/ (+ x y) 2))
}}}{{{#!python
average = lambda x, y: (x+y)/2.0
}}}
 1. {{{
(define (good-enough? guess x)
  (< (abs (- (square guess) x)) 0.001))
}}}{{{#!python
good_enough = lambda guess, x: abs(square(guess)-x)< 0.001
}}}
 1. {{{
(define (sqrt x)
  (sqrt-iter 1.0 x))
}}}{{{#!python
sqrt = lambda x:sqrt_iter(1.0, x)
}}}
 1. {{{
(sqrt 9)
3.00009155413138
(sqrt (+ 100 37))
11.704699917758145
(sqrt (+ (sqrt 2) (sqrt 3)))
1.7739279023207892
(square (sqrt 1000))
1000.000369924366
}}}


=== Procedures as Black-Box Abstractions ===

"SICP的Python实现"版本比较

Building Abstractions with Procedures

1. Procedures and the Processes They Generate