Resolving macro variables

[nimmy_mj]

Hi, I have the below code:

%let a=b;
%let b=c;
%let c=a;

%let d=&c; %let e=&&c; %let f=&&&c; %let g=&&&&c; %let h=&&&&&c; %let i=&&&&&&c;

data test;
check="&d";output;
check="&e";output;
check="&f";output;
check="&g";output;
check="&h";output;check="&i";output;
run;

d resolves to a

e resolves to a

f resolves to b

g resolves to a

h resolves to b

I resolves to b

Could you please explain how this is happening? According to my logic, g should resolve to b and h should resolve to c and I to c.

If there is a diagrammatical representation, it will be helpful.

[data_null__]

[Shmuel]

Pay attention that any && are in first step replaced by &.

&&&X = (&&) &X - (1) resolve &X then resolve &(resolved value)

&&&&X = (&&)(&&)x = &&X = &X

I hope that explains the behavior.

[Tom]

Turn the SYMBOLGEN option and see for yourself what is happening.

1     %let a=b;
2     %let b=c;
3     %let c=a;
4     options symbolgen;
5     %let d=&c;
SYMBOLGEN:  Macro variable C resolves to a
6    %let e=&&c;
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  Macro variable C resolves to a
7    %let f=&&&c;
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  Macro variable C resolves to a
SYMBOLGEN:  Macro variable A resolves to b
8    %let g=&&&&c;
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  Macro variable C resolves to a
9    %let h=&&&&&c;
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  Macro variable C resolves to a
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  Macro variable A resolves to b
10   %let i=&&&&&&c;
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  && resolves to &.
SYMBOLGEN:  Macro variable C resolves to a
SYMBOLGEN:  Macro variable A resolves to b
11   options nosymbolgen;

[ballardw]

You might be better off using %PUT statements to determine the evaluation of your data. The data step you use will set the length of the variable CHECK to the length of the first variable. Which could result in truncation. Please see:

%let a=b;
%let b= somethinglonger;

data test;
check="&a.";output;
check="&b.";output;
run;
proc print data=test;
run;

compare with:

%put A is: &a.;
%put B is: &b.;