topic Re: reverse strings in SAS Programming

reverse strings

BrahmanandaRao — Sat, 10 Dec 2022 11:31:13 GMT

data nnn;
set sashelp.class;
length rev_string $ 25;
do i=1 to length(rev_string);
rev_string=substr(Name,length(Name)-i,1);
end;drop i ;
proc print;run;

how reverse string (Name) where i did wrong in the class dataset

Re: reverse strings

PeterClemmensen — Sat, 10 Dec 2022 11:33:43 GMT

Is this an assignment? Otherwise, why not use the Reverse Function?

Re: reverse strings

ger15xxhcker — Sat, 10 Dec 2022 11:43:32 GMT

The DO loop you wrote is incorrect. To reverse a string, you can use the SAS function REVERSE(). You can use it, like this:
rev_string = reverse(Name);

Re: reverse strings

BrahmanandaRao — Sat, 10 Dec 2022 11:48:18 GMT

Yes Peter

I am trying instead of REVERSE function

Re: reverse strings

PaigeMiller — Sat, 10 Dec 2022 11:55:41 GMT

@BrahmanandaRao wrote:

Yes Peter

I am trying instead of REVERSE function

Why write your own code instead of the REVERSE function?

Re: reverse strings

Astounding — Sat, 10 Dec 2022 13:07:03 GMT

Your DO loop replaces REV_STRING with a single character each time through the loop ... not what is needed. Do you need help in fixing that?

What about blanks? For example, this code contains 7 trailing blanks in STRING:

length string $ 10;
string = 'ABC';
rev_string = reverse(string);

Using the REVERSE function, the result would contain 7 leading blanks followed by "CBA". Are you attempting to replicate that result, or are you intending to ignore the blanks and get "CBA" followed by 7 trailing blanks?

Re: reverse strings

PaigeMiller — Sat, 10 Dec 2022 13:13:34 GMT

@Astounding wrote:

Your DO loop replaces REV_STRING with a single character each time through the loop ... not what is needed. Do you need help in fixing that?

What about blanks? For example, this code contains 7 trailing blanks in STRING:
length string $ 10;
string = 'ABC';
rev_string = reverse(string);
Using the REVERSE function, the result would contain 7 leading blanks followed by "CBA". Are you attempting to replicate that result, or are you intending to ignore the blanks and get "CBA" followed by 7 trailing blanks?

Either of the "problems" caused by spaces in the REVERSE function are easy to fix. Easier than writing your own code.

Re: reverse strings

Astounding — Sat, 10 Dec 2022 14:04:29 GMT

You're absolutely right, the REVERSE function would be easier and more accurate. I'm assuming that this is a homework assignment and the instructor is trying to make that exact point: functions are thoroughly tested and debugged and easier to use when compared to "do it yourself" code.

Re: reverse strings

Kurt_Bremser — Sat, 10 Dec 2022 19:30:00 GMT

Use two index variables: one to count down from length(name) to 1, the other starting at 1 and incrementing in the loop. Then use SUBSTR on the left and right side of the assignment (left for rev_string, right for name).

Re: reverse strings

PeterClemmensen — Sat, 10 Dec 2022 19:45:38 GMT

Also, an opportunity to use the rarely used character format $REVERS Format .