Understanding SAS Macro Language Evaluations: Expressions, Operators, and Comparisons

Session 7, Chapter 6 From SAS 9.3 Macro Language Reference Macro Expressions P 71

&Eval - p 72-73 %let A=2; %let B=5; %let operator=+; %put The result of &A &operator &B is %eval(&A &operator &B).; The result of 2 + 5 is 7.

Macro Language Operators – p 73Table 6.3 • P 73 • ** • + • - • -^~ • etc

The macro facility is a string handling facility – p 74-75 * Use %EVAL in a %LET statement; %let a=%eval(1+2); %let b=%eval(10*3); %let c=%eval(4/2); %let i=%eval(5/3); %put The value of a is &a; %put The value of b is &b; %put The value of c is &c; %put The value of I is &i; ******** Note answers are all integer;

%SYSEVAL p. 75 * USE SYSEVAL INSTEAD; %let a=%sysevalf(10.0*3.0); %let b=%sysevalf(10.5+20.8); %let c=%sysevalf(5/3); %put 10.0*3.0 = &a; %put 10.5+20.8 = &b; %put 5/3 = &c; * Note answers can be floating point now. ;

How Macro Evaluates Logical Expression p 76 %macro compnum(first,second); %if &first>&second %then %put &first is greater than &second; %else %if &first=&second %then %put &first equals &second; %else %put &first is less than &second; %mend compnum; *Invoke the COMPNUM macro with these values; %compnum(1,2) %compnum(-1,0) ; The following results are displayed in the log: 1 is less than 2 -1 is less than 0

Other comparisons • Floating point p 76-77 • Type in the code on top of 77 & test • Compare character operands in logical expressions p 77 • Type in example code middle of p 77 & test

Chapter 7 – Macro Quoting – p 79 • Why doesn’t this work? P 81 %let print=proc print; run;; • Why does this work? %let print=%str(proc print; run;); • What does %str() do?

NRSTR%() - P 88 • Use NRSTR%() when there is a macro variable name in the expression that you don’t want evaluated – this prevents the macro variable from being evaluated %macro example; %local myvar; %let myvar=abc; %put %nrstr(The string &myvar appears in log output,); %put instead of the variable value.; %mend example; %example • The string &myvar appears in log output, • instead of the variable value.

Example 2 %NRSTR • Type in example middle of p 88 %macro credits(d=%nrstr(Mary&Stacy&Joan Ltd.)); footnote "Designed by &d"; %mend credits; • Run with %credits() • Observe output. What happens if you use %SRT instead? Try it.

BQuote p 89 • Use BQUOTE() when an expression has unmatching quotes such as Jones’s • NRBQUOTE() when there is a macro expression you don’t want evaluated + unmatching quotes.

Example BQUOTE – p 90 ** Example BQWUOTE p 90; data test; store="Susan's Office Supplies"; call symput('s',store); run; %macro readit; %if %bquote(&s) ne %then %put *** valid ***; %else %put *** null value ***; %mend readit; %readit ; * Observe output in log – what if you don’t use BQUOTE?;

SuperQ – p 92 ***********EXAMPLE SUPERQ ********AND %WINDOW; * It masks items that might require macro quoting; %window ask #5 @5 'Enter two values:' #5 @24 val 15 attr=underline; %macro a; %put *** This is a. ***; %mend a; %macro test; %display ask; %put *** %superq(val) ***; /* Note absence of ampersand */ %mend test; *invoke the macro TEST; %test

Ch 9, 10 & 11 • Ch 9 - Storing and Reusing Macros – read on your own • Ch 10 – Macro Errors • Note bullets on p 121 • See Note bottom p 129 double and single quotes • Ch 11 – Writing Efficient Code - read on your own

Ch 12 – Macro Language Elements • Review Table 12.1 p 156 • Table 12.2 p 157 • Table 12.3 p 158 • Table 12.4 p 159 • Table 12.5 p 160 • Table 12.9 p 166

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Understanding SAS Macro Language Evaluations: Expressions, Operators, and Comparisons