以下是 factorial 创建的过程对象：
+---------------------------------+
global env --> | |
| factorial --+ |
+--------------|------------------+
| ^
| |
| |
[*][*]----+
|
|
v
parameters: n
body: (if (= n 1)
1
(* n (factorial (- n 1))))
以下是对 (factorial 6) 进行求值时所创建的环境结构（为了节约空间，将 factorial 表示为 f ）：
+---------------------------------+
global env --> | |
| |
+---------------------------------+
^
(f 6) |
|
+------+
| |
E1 -> | n: 6 |
| |
+------+
(* 6 (f 5))
+---------------------------------+
global env --> | |
| |
+---------------------------------+
^ ^
(f 6) | (f 5) |
| |
+------+ +------+
| | | |
E1 -> | n: 6 | E2-> | n: 5 |
| | | |
+------+ +------+
(* 6 (f 5)) (* 5 (f 4))
+--------------------------------------------+
global env --> | |
| |
+--------------------------------------------+
^ ^ ^
(f 6) | (f 5) | (f 4) |
| | |
+------+ +------+ +------+
| | | | | |
E1 -> | n: 6 | E2-> | n: 5 | E3 -> | n: 4 |
| | | | | |
+------+ +------+ +------+
(* 6 (f 5)) (* 5 (f 4)) (* 4 (f 3))
+----------------------------------------------------------+
global env --> | |
| |
+----------------------------------------------------------+
^ ^ ^ ^
(f 6) | (f 5) | (f 4) | (f 3) |
| | | |
+------+ +------+ +------+ +------+
| | | | | | | |
E1 -> | n: 6 | E2-> | n: 5 | E3 -> | n: 4 | E4 -> | n: 3 |
| | | | | | | |
+------+ +------+ +------+ +------+
(* 6 (f 5)) (* 5 (f 4)) (* 4 (f 3)) (* 3 (f 2))
+--------------------------------------------------------------------------+
global env --> | |
| |
+--------------------------------------------------------------------------+
^ ^ ^ ^ ^
(f 6) | (f 5) | (f 4) | (f 3) | (f 2) |
| | | | |
+------+ +------+ +------+ +------+ +------+
| | | | | | | | | |
E1 -> | n: 6 | E2-> | n: 5 | E3 -> | n: 4 | E4 -> | n: 3 | E5 -> | n: 2 |
| | | | | | | | | |
+------+ +------+ +------+ +------+ +------+
(* 6 (f 5)) (* 5 (f 4)) (* 4 (f 3)) (* 3 (f 2)) (* 2 (f 1))
+------------------------------------------------------------------------------------------+
global env --> | |
| |
+------------------------------------------------------------------------------------------+
^ ^ ^ ^ ^ ^
(f 6) | (f 5) | (f 4) | (f 3) | (f 2) | (f 1) |
| | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
| | | | | | | | | | | |
E1 -> | n: 6 | E2-> | n: 5 | E3 -> | n: 4 | E4 -> | n: 3 | E5 -> | n: 2 | E6 -> | n: 1 |
| | | | | | | | | | | |
+------+ +------+ +------+ +------+ +------+ +------+
(* 6 (f 5)) (* 5 (f 4)) (* 4 (f 3)) (* 3 (f 2)) (* 2 (f 1)) 1
以下是 factorial 创建的过程对象：
+----------------------------------------------------------+
global env --> | |
| factorial --+ fact-iter --+ |
+--------------|-----------------------------|-------------+
| ^ | ^
| | | |
| | | |
[*][*]----+ [*][*]-----+
| |
| |
v v
parameters: n parameters: product counter max-count
body: (fact-iter 1 1 n) body: (if (> counter max-count)
product
(fact-iter (* counter product)
(+ counter 1)
max-count))
以下是对 (factorial 6) 求值时所创建的环境结构（为了节约空间， factorial 表示为 f ， fact-iter 表示为 i ， product 表示为 p ， counter 表示为 c ， max-count 表示为 m ）：
+----------+
global | |
env --> | |
| |
+----------+
^
(f 6) |
|
+-------+
| |
E1 -> | n: 6 |
| |
+-------+
(i 1 1 6)
+---------------------------+
global | |
env --> | |
| |
+---------------------------+
^ ^
(f 6) | (i 1 1 6) |
| |
+-------+ +-------+
| | | p: 1 |
E1 -> | n: 6 | E2 -> | c: 1 |
| | | m: 6 |
+-------+ +-------+
(i 1 1 6) (i 1 2 6)
...... 中间部分省略
+-----------------------------------------------------------------------------------------------------------------------------+
global | |
env --> | |
| |
+-----------------------------------------------------------------------------------------------------------------------------+
^ ^ ^ ^ ^ ^ ^ ^
(f 6) | (i 1 1 6) | (i 1 2 6) | (i 2 3 6) | (i 6 4 6) | (i 24 5 6) | (i 120 6 6) | (i 720 7 6) |
| | | | | | | |
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
| | | p: 1 | | p: 1 | | p: 2 | | p: 6 | | p: 24 | | p:120 | | p:720 |
E1 -> | n: 6 | E2 -> | c: 1 | E3 -> | c: 2 | E4 -> | c: 3 | E5 -> | c: 4 | E6 -> | c: 5 | E7 -> | c: 6 | E8 -> | c: 7 |
| | | m: 6 | | m: 6 | | m: 6 | | m: 6 | | m: 6 | | m: 6 | | m: 6 |
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
(i 1 1 6) (i 1 2 6) (i 2 3 6) (i 6 4 6) (i 24 5 6) (i 120 6 6) (i 720 7 6) 720