Question

#define F(x) x - 2 #define D(x) x*F(x) printf("%d,%d", D(3), D(D(3))) ;

Answer 1

7,-13
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(1)
F(x) = x - 2; 注意，按定义，不带括号。
D(x) = x*x-2
D(3) = 3*3-2 = 7
(2)
D(D(3)) 把 D(3) 先看成D(x) 或 X, 把3看成x, 考虑如何一步步做宏替代
X = x*x-2;
D(D(x)) = D(X) = X * X - 2
D(D(x)) = x*x-2 * x*x-2 -2 = 3*3 - 2*3*3-2 -2； 由于无括号，运算时先乘除后加减
= 9 - 18 -2 -2 = -13