2 %let L2=L3;
3 %let L3=L4;
4 %let L4=L5;
5
6 %put &L1;
结果:L2
7 %put &&L1;
结果:L2
过程:&&L1 -> &L1 -> L2
8 %put &&&L1;
结果:L3
过程:&&&L1 -> &L2 -> L3
9 %put &&&&L1;
结果:L2
过程:&&&&L1 -> &&L1 -> &L1 -> L2
10 %put &&&&&L1;
结果:L3
过程:&&&&&L1 -> &&L2 -> &L2 -> L3
11 %put &&&&&&L1;
结果:L3
过程:&&&&&&L1 -> &&&L1 -> &L2 -> L3
12 %put &&&&&&&L1;
结果:L4
过程:&&&&&&&L1 -> &&&L2 -> &L3 -> L4
13 %put &&&&&&&&L1;
结果:L2
过程:&&&&&&&&L1 -> &&&&L1 -> &&L1 -> &L1 -> L2
14 %put &&&&&&&&&L1;
结果:L3
过程:&&&&&&&&&L1 -> &&&&L2 -> &&L2 -> &L2 -> L3
15 %put &&&&&&&&&&L1;
结果:L3
过程:&&&&&&&&&&L1 -> &&&&&L1 -> &&L2 -> &L2 -> L3
========= SAS 代码 =========
options symbolgen;
%let L1=L2;
%let L2=L3;
%let L3=L4;
%let L4=L5;
%put &L1;
%put &&L1;
%put &&&L1;
%put &&&&L1;
%put &&&&&L1;
%put &&&&&&L1;
%put &&&&&&&L1;
%put &&&&&&&&L1;
%put &&&&&&&&&L1;
%put &&&&&&&&&&L1;
========= SAS 日志 =========
5780 options symbolgen;
5781
5782 %let L1=L2;
5783 %let L2=L3;
5784 %let L3=L4;
5785 %let L4=L5;
5786
5787 %put &L1;
SYMBOLGEN: Macro variable L1 resolves to L2
L2
5788 %put &&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
L2
5789 %put &&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
SYMBOLGEN: Macro variable L2 resolves to L3
L3
5790 %put &&&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
L2
5791 %put &&&&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L2 resolves to L3
L3
5792 %put &&&&&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
SYMBOLGEN: Macro variable L2 resolves to L3
L3
5793 %put &&&&&&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L2 resolves to L3
SYMBOLGEN: Macro variable L3 resolves to L4
L4
5794 %put &&&&&&&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
L2
5795 %put &&&&&&&&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L2 resolves to L3
L3
5796 %put &&&&&&&&&&L1;
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L1 resolves to L2
SYMBOLGEN: && resolves to &.
SYMBOLGEN: Macro variable L2 resolves to L3
L3



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