SAS 9.4 Macro Language: Reference, Fourth Edition, 4th Edition

You can end any macro variable reference with a delimiter, but the delimiter is necessary

only if the characters that follow can be part of a SAS name. For example, both of these

TITLE statements are correct:

title "&name.--a report";

title "&name--a report";

They produce the following:

TITLE "sales--a report";

Displaying Macro Variable Values

The simplest way to display macro variable values is to use the %PUT statement, which

writes text to the SAS log. For example, the following statements write the following

result:

%let a=first;

%let b=macro variable;

%put &a ***&b***;

Here is the result:

first ***macro variable***

You can also use a “%PUT Statement” on page 325 to view available macro variables.

%PUT provides several options that enable you to view individual categories of macro

variables.

The system option SYMBOLGEN displays the resolution of macro variables. For this

example, assume that macro variables PROC and DSET have the values GPLOT and

Sasuser.Houses, respectively.

options symbolgen;

title "%upcase(&proc) of %upcase(&dset)";

The SYMBOLGEN option prints to the log:

SYMBOLGEN: Macro variable PROC resolves to gplot

SYMBOLGEN: Macro variable DSET resolves to sasuser.houses

For more information about debugging macro programs, see Chapter 10, “Macro Facility

Error Messages and Debugging,” on page 119.

Referencing Macro Variables Indirectly

Using an Expression to Generate a Reference

The macro variable references shown so far have been direct macro references that begin

with one ampersand: &name. However, it is also useful to be able to indirectly reference

macro variables that belong to a series so that the name is determined when the macro

variable reference resolves. The macro facility provides indirect macro variable

referencing, which enables you to use an expression (for example, CITY&N) to generate

a reference to one of a series of macro variables. For example, you could use the value of

macro variable N to reference a variable in the series of macro variables named CITY1

Referencing Macro Variables Indirectly 33

to CITY20. If N has the value 8, the reference would be to CITY8. If the value of N is 3,

the reference would be to CITY3.

Although for this example the type of reference that you want is CITY&N, the following

example will not produce the value of &N appended to CITY:

%put &city&n; /* incorrect */

This code produces a warning message saying that there is no macro variable CITY

because the macro facility has tried to resolve &CITY and then &N and concatenate

those values.

When you use an indirect macro variable reference, you must force the macro processor

to scan the macro variable reference more than once. This process will resolve the

desired reference on the second, or later, scan. To force the macro processor to rescan a

macro variable reference, you use more than one ampersand in the macro variable

reference. When the macro processor encounters multiple ampersands, its basic action is

to resolve two ampersands to one ampersand. For example, for you to append the value

of &N to CITY and then reference the appropriate variable name, do the following:

%put &&city&n; /* correct */

If &N contains 6, when the macro processor receives this statement, it performs the

following steps:

1. resolves && to &

2. passes CITY as text

3. resolves &N into 6

4. returns to the beginning of the macro variable reference, &CITY6, starts resolving

from the beginning again, and prints the value of CITY6

Generating a Series of Macro Variable References with a Single

Macro Call

Using indirect macro variable references, you can generate a series of references with a

single macro call by using an iterative %DO loop. The following example assumes that

the macro variables CITY1 through CITY10 contain the respective values Cary, New

York, Chicago, Los Angeles, Austin, Boston, Orlando, Dallas, Knoxville, and Asheville:

%macro listthem;

%do n=1 %to 10; &&city&n

%end;

%mend listthem;

%put %listthem;

This program writes the following to the SAS log:

Cary New York Chicago Los Angeles Austin Boston

Orlando Dallas Knoxville Asheville

Using More Than Two Ampersands

You can use any number of ampersands in an indirect macro variable reference, although

using more than three is rare. Regardless of how many ampersands are used in this type

of reference, the macro processor performs the following steps to resolve the reference.

34 Chapter 3 • Macro Variables