Re: Using %scan and %subst vs pointers

[Sam_L <lennon_s_j@xxxxxxxxxxx>]

When it comes to efficiency, I always want to know how often this is 
going to be run:  10's, 1000's, millions of time per mintue, per hour, 
what? Rule of thumb, don't sweat the small stuff.

If maximum performance is required, test different approaches on a large 
set of data.

Having said that, if I had to do it for maximum efficiency, I'd probably 
use the pointer approach. but I'm very comfortable with pointers.

Off the top of my head, I'd probably write a procedure that was passed 
the initial string as a variable string, and an index to where to start 
searching (the x'1c') for the end markers.  It would return the 
extracted string and an index to the next x'1c', or zero if this was the 
end.

Then in an outer loop I'd call this procedure until zero is returned,

So internally in the procedure you can experiment with various 
techniques to see what is the most efficient.

On a totally different approach, you might look at the %SPLIT BIF.

Sam


On 6/3/2022 12:04 PM, Vinay Gavankar wrote:
> Hi,
>
> I was trying to write a routine to get a value of a field from a string.
> The field starts with an identifier, which is x'1c' + 2 characters. The
> field ends when either a new field starts with either x'1c', x'1d' or
> x'1e', or if it is the last field in the string, it would have all spaces
> after it.
>
> Would it be more efficient to use %scan to find the start and end positions
> and then %subst to extract the value, or use some sort of pointer code to
> go thru the string character by character to do my own search? Or use a
> combination of both?
>
> My first scan to find the start of the field is simple. But to get the end
> of field, I will have to do multiple %scans for each of the 3 possible
> characters (unless I am missing something).
>
> So would it be better to use %scan to find the start of the field, and then
> use pointers to find the end.
>
> I have never used pointers for this kind of thing, but I think it should be
> possible.
>
> Any thoughts or suggestions would be appreciated.
> TIA
> Vinay