执行以下两段程序1.%let mv=shoes;
%macro product(td=bicycles);
%let mv = clothes;
%let td = opp;
%mend;
%product(td = tens)
%put mv is &mv;
结果:mv is clothes
2.%let mv=shoes;
%macro product(mv=bicycles);
%let mv = clothes;
%mend;
%product(mv = tens)
%put mv is &mv;
结果:mv is shoes
请问能帮解释下结果吗?对于程序1,mv已经在宏定义之外定义了,在全局变量表中了,为什么结果还是clothes啊
谢谢啦