3.1.4逻辑运算 (ch>='a'&&ch<='z')l(ch>='A'&&ch<='Z) ch>='0'&&ch<='9' x<=1关系运算 -1<=X<=1 0 -1 1 X X>=-1并且X<=1 X>=-1&&X<=13.1.4 逻辑运算 (ch >= 'a' && ch <= 'z' ) || ( ch >= 'A' && ch <= 'Z') ch >= '0' && ch <= '9' x<=1 关系运算 -1 <= x <= 1 0 -1 1 x x >= -1 并且 x <= 1 x >= -1 && x <= 1