topic Re: How to validate arithmetic/mathematical expressions in SAS in SAS Programming

How to validate arithmetic/mathematical expressions in SAS

Azeem112 — Sun, 20 Sep 2020 09:47:42 GMT

I want to validate arithmetic/Mathematical expressions. expression is a string that can be given to program via any file or via datalines/cards.

data test;
length expression $15;
input expression $;
datalines;                      
(10+5)/(10-7)
1+2
2-3/4
(6-10)*6
c-10
10+-5
10/0
(10-40-)10
(K100-50)/10
(10+50)15
10*/5
;
run;

from the above expression some are correct and few are incorrect. I want to validate each expression as

Below is what I thought and tried

data validation;

set test;

length validate 8;

validate = function(expresssion);

run;

function can be any macro or function that runs that executes the expression and saves the input in validate. if the value of validate is not empty than the expression is correct else the expression is incorrect.

I've tried

validate = put(expression , 8.);
validate = expression;

but it's not working as expected.

below is the expression validation

"(10+5)/(10-7)" */Correct/*
"1+2" */Correct/*
"2-3/4" */Correct/*
"(6-10)*6" */Correct/*
"c-10" */InCorrect/*
"10+-5" */Correct/*
"10/0" */InCorrect/*
"(10-40-)10" */InCorrect/*
"(K12 - 50)/10" */InCorrect/*
"(100+50)15" */InCorrect/*

"10*/5" */InCorrect/*

Kindly provide an approach to validate arithmetic expressions that are stored in character variables.

Thanks.

Re: How to validate arithmetic/mathematical expressions in SAS

Ksharp — Sat, 19 Sep 2020 13:45:54 GMT

This could give you a clue .

data test;
length expression $15;
input expression $;
result=resolve(cats('%sysevalf(',expression,')'));
datalines;                      
(10+5)/(10-7)
1+2
2-3/4
(6-10)*6
c-10
10+-5
10/0
(10-40-)10
(K100-50)/10
(10+50)15
;
run;

Re: How to validate arithmetic/mathematical expressions in SAS

ballardw — Sat, 19 Sep 2020 17:23:35 GMT

I will beg to differ on these:

"c-10" */InCorrect/* :<= this would be variable C subtracting 10. Why is this incorrect?

"10+-5" */InCorrect/* :<= this is 10 plus a negative 5

4    data junk;
5       x = 10+-5;
6    run;

NOTE: The data set WORK.JUNK has 1 observations and 1 variables.
NOTE: DATA statement used (Total process time):
      real time           0.01 seconds
      cpu time            0.00 seconds

and yields the expected value of 5

"(K12 - 50)/10" */InCorrect/ :<= variable K12 minus 50, the quantity divided by 10. So why is this incorrect. If the variable K12 is not defined then 1) just created it, 2) effectively assigned a missing value and 3) a missing value results from the expression. Note the log below shows 2 variables in the output data.

11   data junk;
12      y=(K12 - 50)/10;
13   run;

NOTE: Variable K12 is uninitialized.
NOTE: Missing values were generated as a result of performing
      an operation on missing values.
      Each place is given by:
      (Number of times) at (Line):(Column).
      1 at 12:11
NOTE: The data set WORK.JUNK has 1 observations and 2 variables.
NOTE: DATA statement used (Total process time):
      real time           0.00 seconds
      cpu time            0.00 seconds

If this is for a grammar other than SAS you need to be much more explicit about why these are incorrect, and SAS may not be the tool to evaluate.

Re: How to validate arithmetic/mathematical expressions in SAS

Azeem112 — Sun, 20 Sep 2020 09:46:14 GMT

Regarding "C-10" and "(K12 - 50)/10" are incorrect because variables are not allowed and system don't ave values for these variables. just numeric arithmetic expression.

Regarding 10+-5 is correct, I've edited the post. however 10+*5 or 10/*5 where two operators are coming together except "10+-5", "10*-5" and "10/-5" are incorrect.

Thanks.