Building Abstractions with Procedures

Include(/SICP的Python实现1.1) Include(/SICP的Python实现1.2) Include(/SICP的Python实现1.3)

Building Abstractions with Data

Modularity, Objects, and State

Metalinguistic Abstraction

Computing with Register Machines

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+参考文献：http://mitpress.mit.edu/sicp/full-text/book/book.html
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-== The Elements of Programming ==
=== Expressions ===
 1. {{{
486
}}}{{{#!python
486
}}}
+[[Include(/SICP的Python实现1.1)]]
[[Include(/SICP的Python实现1.2)]]
[[Include(/SICP的Python实现1.3)]]
= Building Abstractions with Data =
= Modularity, Objects, and State =
= Metalinguistic Abstraction =
= Computing with Register Machines =
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+行号 13:
-. {{{
(+ 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 ===

== 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
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"SICP的Python实现"版本比较

Building Abstractions with Procedures

Building Abstractions with Data

Modularity, Objects, and State

Metalinguistic Abstraction

Computing with Register Machines