adv 130 中80 多谢

80. The following SAS program is submitted:
%let rc = Begin;
%macro test;
data out;
set sashelp.prdsale nobs = totalobs;
if totalobs > 10 then do;
%let rc = high;
end;
else do;
%let rc = low;
end;
run;
%mend;
%let rc = Before Execution;
%test
The data set SASHELP.PRDSALE has 50 observations.
What is the value of the variable RC when the macro finishes execution?
A.low
B.high
C.Begin
D.Before Execution

I think it Should be D because &RC is got global.

But why don't you run it in sas? You will have a definitive answer. Playing with is the best way to learn it.
----- updated: my previous answer is incorrect. According to sas document, macro variables defined outside of any macro are global. So in this case, the value should be assigned by the last time %let statement is used.

Sorry for the wrong answer.

johnpark1 发表于 2015-11-3 00:57
I think it Should be D because &RC is got global.

But why don't you run it in sas? You will have ...

已经上机跑了，答案是low，就是没想明白为什么是这个。

这里有2个变量RC，一个是global, 一个是local.

在macro结束运行的时侯，local 的 RC是low，但是global 的 RC 是Before Execution。题目问的应该是local RC的值。

”Since local symbol tables exist separately from the global symbol table, it is possible to have a local macro variable and a global macro variable that have the same name and different values.”

mandyfervor 发表于 2015-11-3 03:34
已经上机跑了，答案是low，就是没想明白为什么是这个。

See my correction above.

stayhungry05 发表于 2015-11-3 12:01
这里有2个变量RC，一个是global, 一个是local.

在macro结束运行的时侯，local 的 RC是low，但是global  ...

local的怎么就是low呢？ totalobs是50 是大于10的，那也应该是运行第一个也就是rc=high啊。
我在想是不是因为是%let 是定义global变量的，所以不受condition的限制。

mandyfervor 发表于 2015-11-4 05:57
local的怎么就是low呢？ totalobs是50 是大于10的，那也应该是运行第一个也就是rc=high啊。
我在想是不是 ...

%let是macro statement 在你的data step 运行之前就已经执行了 data step的逻辑对它没有任何影响