Re: RPGLE pgm to parse a string

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

Wouldn't it be faster to call %SCAN in a loop rather than using SCAN 
folloed by LOOKUP?  Seems to me that both SCAN and LOOKUP run loops under 
the covers.  That being the case, if you write your own %SCAN loop, you 
only have to loop through the array once.  If you call SCAN followed by 
LOOKUP, then you've looped through it twice.  Seems like %SCAN would be 
faster.

The other problem with your solution is that it scans from the left-hand 
side.  Sure, it'd work, but wouldn't it be faster to scan from the right 
hand side, and abort the process as soon as you found the last underscore 
you needed?  The way you're doing it, it finds every single underscore in 
the string, and that seems like overkill to me.

Just my opinion, of course.

---
Scott Klement  http://www.scottklement.com


On Wed, 5 Apr 2006, Terry Richardson wrote:

> I didn't see anyone mention using the SCAN op code.  I know, everyone here
> seems to think /free is a must, but the %scan BIF is lacking something the
> good old op code gave us.  You can populate an array with the positions of a
> search argument with a string using the SCAN op code.
>
> Take the following string.
>
> 'my_string_to_be_scanned_and_fill_array_with_positions_where_underscore_is'
>
> Using the following:
>
> C     '_'           SCAN      ScanString    Array
>
> The resulting array will contain the values
> 3,10,13,16,24,28,33,39,44,54,60,71,0,0,0,0,0,0,0,......
>
> The number of elements in Array must equal the number of characters in
> ScanString.
>
> So to get the word 'where' as you requested, take the resulting array, do a
> LOOKUP for the first occurrence of a zero value, and subtract 2 from the
> index, save the element value in Y, subtract one more from the index, save
> the element value in X, then use the following to get the string you want:
>
> C                   EVAL      WhatIWant = %subst(ScanString:X+1:Y-1)
>
> Note:  I have not tested this, just did this off the top of my head.
> ****************************************