个人感觉在 SAS 宏语言里最难掌握或者最易混淆的就是各种 QUOTE 函数的用法，刚好上周五帮同事看了一个跟QUOTE 相关的问题，借此机会将 QUOTE 的作用以及所有 QUOTE 函数的用法整理如下。

这是几位 SAS 用户在 SGF Paper 里面对 Macro Quoting 的感慨：

I have often said that anyone who thinks macro quoting is simple, probably doesn't understand the problem. 

Macro quoting is hard because:
• Quoting is inherently a hard subject.
• The interaction between two languages makes quoting harder.
• The timing issues involved are complex, when the generated language compiles and executes during the
generation of its code.
• There are two macro languages involved - the one which is compiled between %MACRO and %MEND
statements and the one which executes immediately in open SAS code.
• Bugs in the macro facility prevent recognition of a consistent pattern of how macro quoting works.

原文 http://support.sas.com/resources/papers/proceedings10/029-2010.pdf

For programmers new to the SAS® Macro Facility, understanding the set of Macro quoting functions and their appropriate uses can be a difficult task. 

原文 http://www2.sas.com/proceedings/forum2007/152-2007.pdf

一、为什么要 QUOTE ?

如果你的宏变量取值中包含特殊字符，比如 ; & % ' ( ) 等，那么你必须使用 QUOTE 函数，否则 SAS 代码执行时会出现语法错误、大量宏变量无法替换的警告信息、甚至错误结果。另外，如果你的代码需要在宏语言中处理包含中文字符的 http 链接，那么通常情况下你需要使用 QUOTE 函数。

比如下面的例子中，我们需要对四个宏变量赋值：

%let var1=a=1;b=2;;
%let var2=a&b;
%let var3=&var2;
%let var4=&var1&var2;

%put &var1;
%put &var2;
%put &var3;
%put &var4;

SAS 执行结果：

119  %let var1=a=1;b=2;;
                   -
                   180
ERROR 180-322: Statement is not valid or it is used out of proper order.

WARNING: Apparent symbolic reference B not resolved.
120  %let var2=a&b;
121  %let var3=&var2;
WARNING: Apparent symbolic reference B not resolved.
122  %let var4=&var1&var2;
WARNING: Apparent symbolic reference B not resolved.
WARNING: Apparent symbolic reference B not resolved.
123  %put &var1;
a=1
124  %put &var2;
WARNING: Apparent symbolic reference B not resolved.
a&b
125  %put &var3;
WARNING: Apparent symbolic reference B not resolved.
a&b
126  %put &var4;
WARNING: Apparent symbolic reference B not resolved.
WARNING: Apparent symbolic reference B not resolved.
a=1a&b （注意：此结果不对）

正确的结果应当是：

132  %put &var1;
a=1;b=2;
133  %put &var2;
a&b
134  %put &var3;
a&b
135  %put &var4;
a=1;b=2;a&b

二、QUOTE 函数原理及其用法

QUOTE 函数的作用是屏蔽这些特殊字符，使得 SAS 系统把这些特殊字符当成普通字符来看待。

背后的原理如下：SAS 系统所有的宏变量及其取值都存在一张表中，对于使用了 QUOTE 的字符 SAS 在存储时会给这些特殊字符加上前缀和后缀，SAS 宏处理器对该宏变量做字符串替换时把前缀和后缀去掉，用其原始值来完成替换。

三、样例代码

大家可以执行下面的代码，看看使用不同 QUOTE 函数得到的结果。

有问题的样例代码： 

%let var1=%str(a=1;b=2;);
%let var2=%str(a&b);
%let var3=%str(&var2);
%let var4=%str(&var1&var2);

%put &var1;
%put &var2;
%put &var3;
%put &var4;

%let var1=%nrstr(a=1;b=2;);
%let var2=%nrstr(a&b);
%let var3=%nrstr(&var2);
%let var4=%nrstr(&var1&var2);

%put &var1;
%put &var2;
%put &var3;
%put &var4;

正确的样例代码：
%let var1=%str(a=1;b=2;);
%let var2=%nrstr(a&b);
%let var3=%bquote(&var2);
%let var4=%bquote(&var1&var2);

%put &var1;
%put &var2;
%put &var3;
%put &var4;

有问题的样例代码：

data _null_;
 call symputx('var1', 'a=1;b=2;');
 call symputx('var2', 'a&b');
run;

%let var3=%bquote(&var2);
%let var4=%bquote(&var1&var2);

%put &var1;
%put &var2;
%put &var3;
%put &var4;

正确的样例代码：
data _null_;
 call symputx('var1', 'a=1;b=2;');
 call symputx('var2', 'a&b');
run;
%let var1=%superq(var1);
%let var2=%superq(var2);
%let var3=%nrbquote(&var2);
%let var4=%nrbquote(&var1&var2);

%put &var1;
%put &var2;
%put &var3;
%put &var4;