topic Re: IF ... THEN ... followed by AND in SAS Programming

IF ... THEN ... followed by AND

stechafle — Mon, 13 May 2019 22:19:18 GMT

Why does the first IF Statement below not produce an Error?

data test;
x=0; y=1;

if x=0 then z=0
and y=0;

if x=0
and y=0 then w=0;
run;

proc print data=test;
run;

Re: IF ... THEN ... followed by AND

PGStats — Mon, 13 May 2019 22:44:03 GMT

With SAS the equal sign can be an asignment or an equality operation. z = ... is and assignment because it occurs at the beginning of the statement, but y=0 is an equality operation. SAS represents logical (boolean) values with zeros and ones, 0 = FALSE, 1 = TRUE. The expression

z=0 and y=0

is computed as

z = (0 and (y=0))

z = (0 and (1=0)) /* because y = 1 */

z = (0 and 0) /* because 1=0 is FALSE */

z = 0 /* Because FALSE and FALSE is FALSE */

Re: IF ... THEN ... followed by AND

ballardw — Mon, 13 May 2019 23:11:20 GMT

@stechafle wrote:

Why does the first IF Statement below not produce an Error?

data test;
x=0; y=1;

if x=0 then z=0
and y=0;

if x=0
and y=0 then w=0;
run;

proc print data=test;
run;

If the intent of the first if is to assign values to both Z and Y the code would be:

if x= 0 then do;

z=0;

y=0;

end;

Re: IF ... THEN ... followed by AND

Tom — Mon, 13 May 2019 23:58:48 GMT

What error should it produce?

Note that the compiler cannot read your mind to know whether it is what you intended or not.

Re: IF ... THEN ... followed by AND

VDD — Tue, 14 May 2019 00:18:28 GMT

think about it,

draw pictures with lines results.

then ask yourself do we give order in that manner?

no we give clear and understandable orders so a computer understands what the hay you are thinking.

Re: IF ... THEN ... followed by AND

Kurt_Bremser — Tue, 14 May 2019 10:50:53 GMT

if x=0 then z=0
and y=0;

translates to

if (x = 0) then z = (0 and (y = 0));

(0 and (y = 0)) is a valid numeric expression, and once you look at that, you can see that z will always be set to zero if the condition "x equals zero" is met.

Re: IF ... THEN ... followed by AND

stechafle — Thu, 16 May 2019 16:06:56 GMT

Thank you Kurt! Your explanation makes perfect sense.