1.递增/递减运算符等价式
a=b++;
<=> a=b;b=b+1;
a=++b; <=> b=b+1;b=b;
a=b--; <=> a=b;b=b-1;
a=--b; <=> b=b-1;b=b;
所以，a=5;b=6;var3=a++*--b，结果为25
2.带操作的赋值运算符等价式
a*=b; <=> a=a*b;
a/=b; <=> a=a/b;
a+=b; <=> a=a+b;
a-=b; <=> a=a-b;
a%=b; <=> a=a%b;
a&=b; <=> a=a&b; //从&=开始，下边都是逐位运算符
a|=b; <=> a=a|b;
a^=b; <=> a=a^b;
a>>=b; <=> a=a>>b;
a<<=b; <=> a=a<
<=> a=a>>b; //C#没有此运算符
