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PharmaSUG 2018 - Paper BB-20

The Fundamentals of Macro Quoting Functions

Arthur Li, City of Hope National Medical Center, Duarte, CA

ABSTRACT

The Macro quoting functions is one of the most difficult concepts to grasp when one learns to write a macro program.

One of the reasons for its complexity is closely related to understanding the macro processing, such as macro

compilation and execution phases. Furthermore, the situations for utilizing macro quoting functions are not obvious

for programmers. In this talk, in addition to reviewing the macro processing, we will examine the most useful macro

quoting functions via various examples.

INTRODUCTION

The macro language is a character-based language. That means even numeric values are treated as characters by

the macro processor. The purpose of using the macro language is used to generate SAS codes based on our

instruction. For example, when we write characters such as % and & signs, which are used to signal the macro

processor to perform tasks such as creating macro variables, retrieving values of macro variables, and calling macro.

But in some situations, & and % signs need to be treated simply as texts. The mnemonics, such as OR or GE, are

operators in macro language expressions. In some situations, these special characters or mnemonics only need to be

interpreted as texts as well. Therefore, we need to use the macro quoting functions to mask the special meanings so

that the macro processor will be able to interpret them correctly.

WHY DO WE NEED TO USE THE QUOTING FUNCTIONS?

Here’re a couple of situations where the macro quoting is needed. For example, to create a macro variable, we can

use the %LET statement. The following example attempts to store “proc print data=foo; run;” in the macro

variable &PRINT_FOO.

Code Chunk 1:

%let print_foo = proc print data=foo; run;;

%put &print_foo;

SAS Log:

216 %let print_foo = proc print data=foo; run;;

217 %put &print_foo;

proc print data=foo

The macro variable &PRINT_FOO is not created as we intended and it only stores the value of “proc print

data=foo” since the macro processor treats the first semicolon, which is after “foo”, as the end of the %LET

statement. In this situation, we need to mask the meaning of the semicolons and let the macro processor treat the

semicolons simply as text.

In the following example, the macro variable &NAME stores the value of “Doe, John”. In the second %LET statement,

&NAME needs to be resolved first in the %SUBSTR function. However, the resolution of &NAME contains a comma

which creates a function call that contains four arguments. We need to mask the meaning of commas to prevent the

macro processor from misinterpreting the comma in the resolved values as a separator for the %SUBSTR function.

Code Chunk 2:

%let name = Doe, John;

%let initial = %substr(&name, 1, 1);

%put &initial;

SAS Log:

228 %let name = Doe, John;

229 %let initial = %substr(&name, 1, 1);

ERROR: Macro function %SUBSTR has too many arguments.

230 %put &initial;

The Fundamentals of Macro Quoting Functions, continued

TYPES OF MACRO QUOTING FUNCTIONS

During the macro processing, we need to let the macro processor use the macro quoting functions to mask the

following characters and mnemonics:

& % blank , ; + - * / < > =

┑

^ ~ # | ' " ( )

AND OR NOT EQ NE LE LT GE GT IN

These quoting functions can be categorized into compilation and execution quoting functions.

The compilation quoting functions are %STR and %NRSTR. This type of quoting function is used when a user types

special characters in the open code, such as in the %LET or %PUT statements. They can also be used in a

programming logic statement such as %IF statement. And we use these functions when a user supplies parameter

values on a macro call. During the macro compilation phase, using the compilation quoting functions will treat

characters as text in the macro program.

Other than the %STR and %NRSTR functions, other macro quoting functions are mostly used during the macro

execution. During the macro execution, the execution macro functions mask resolved values from macro variables.

The macro quoting functions generally come in pairs. The function that begins with NR, such as %NRSTR masks all

the special characters listed above. The function that does not begin with NR, such as %STR, masks the special

characters except for ampersands (&) and percent signs (%). The letters NR are short for “non-resolved”. The

function that starts with NR prevents macro or macro variable resolution.

There are also functions that with letter B (for “by itself”), such as %BQUOTE and %NRBQUOTE, which are useful

for quoting unmatched quotation marks or parentheses.

COMPILATION QUOTING FUNCTIONS

The %STR and %NRSTR functions mask special characters and mnemonics during the macro compilation phase.

%STR(character-string)

%NRSTR(character-string)

Both functions mask the special character or mnemonics that are listed above, except that the %STR function does

not mask & and %. When masking ' " ( ), we need to place a percent sign (%) in front of these characters.

THE %STR FUNCTION

The example in Code Chunk 1 can be modified by using the %STR function. The %STR function in Code Chunk 3

masks the meaning of semicolons and the macro processor treats the semicolons within the %STR function as texts.

Code Chunk 3:

%let print_foo = %str(proc print data=foo; run;);

&print_foo

SAS Log:

235

236 %let print_foo = %str(proc print data=foo; run;);

237 &print_foo

NOTE: There were 1 observations read from the data set WORK.FOO.

NOTE: PROCEDURE PRINT used (Total process time):

real time 0.10 seconds

cpu time 0.01 seconds

The following macro FIRST_LAST is used to separate first and last name of a given full name. The full name is

separated by using a comma, which is argument value for the FRIST_LAST macro. The two %LET statements are

used to create two macro variables by using the %SCAN function to extract the first and last name of the macro

variable &NAME, which is the parameter of the FIRST_LAST macro. The default separator, which is including a

comma, is used as the separator for the %SCAN function.

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