SAS Adv 50题的第17题 多个&&的问题

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The following SAS program is submitted:
%let sun=SHINE;
%let shine=MOON;
proc print data=weather(keep=sun shine moon);
sum &&&&sun;
run;
Which one of the following variables is summed in the resulting report?
Correct answer: c
a. sun
b. MOON
c. SHINE
d. None, an ERROR message will be written to the log.

选C，解释是When the macro processor encounters multiple ampersands preceding a macro variable
reference, it resolves two ampersands into one ampersand and re-scans the reference. In this
example, the macro processor resolves the reference &&&&sun to &&sun on the first scan. Then,
the macro processor re-scans and resolves the reference to &sun, and re-scans again, finally
resolving the reference to SHINE.

在sas里跑了一下，2，4，8，16个的时候 结果是Shine，3，5，6，9，10个&的时候结果是moon。7或者14个& 的时候结果是&moon 请问为什么只有7 是不同的呢？怎么解析的呢？

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关键词：encounters Reference Processor following Resolving

xiaojing20 发表于 2019-4-9 11:08
The following SAS program is submitted:
%let sun=SHINE;
%let shine=MOON;

7个&amp;<br>
&amp;&amp;&amp;&amp;&amp;&amp;&amp;sun，首先解析成&amp;&amp;&amp;shine (前六个&amp;解析成三个&amp;，第七个&amp;和sun, 也就是&amp;sun解析成shine)，<br>
第二次解析成&amp;moon(前俩&amp;解析成一个&amp;，后面的&amp;shine解析成moon)，<br>
但是没有对于moon的定义，所以无法进一步解析，也就是&amp;moon