ABAP_to_the_Future

2
New Language Features in ABAP 7.4
2.6.6 New Functions for Common Internal Table Tasks
When working in ABAP code, there are cases in which you want to know in
exactly what line of an internal table the data you are interested in lives. To find
this information out in pre-7.4 ABAP, you would have written code that declared
a helper variable to store the row number of the target record, read the table for
no other purpose than to find that row number, and then transferred the system
variable that contained the result of the table read into your helper variable. An
example of this is shown in Listing 2.57.
DATA: ld_tabix TYPE sy-tabix.
READ TABLE lt_monsters WITH KEY monster_number = ld_monster_
number TRANSPORTING NO FIELDS.
IF sy-subrc = 0.
ld_tabix = sy-tabix.
ENDIF.
Listing 2.57 Reading an Internal Table to Get the Row Number
You see the logic in Listing 2.57 a lot when processing nested loops—you follow
such code with a LOOP AT itab STARTING AT ld_tabix —but also in a myriad of
other use cases. In any event, in release 7.4 this can be simplified by using the
built-in function LINE_INDEX, which does the exact same task but without the
need for looking at the values of SY-SUBRC and SY-TABIX (STARTING AT LINE_
INDEX, etc.). This is shown in Listing 2.58.
DATA(ld_tabix) =
LINE_INDEX( lt_monsters[ monster_number = ld_monster_number] ).
LOOP AT lt_monsters STRTING AT ld_tabix.
Listing 2.58 LINE_INDEX
Throughout this chapter, one aim has been to get rid of helper variables. Because
LINE_INDEX is a so-called built-in function, it can be used at operand positions,
thus negating the need for the helper variable LD_TABIX. So when looping at an
internal table from the row formerly stored in LD_TABIX instead, use the code
shown in Listing 2.59.
LOOP AT lt_monsters STARTING AT LINE_INDEX(etc)
Listing 2.59 Built-In Function LINE_INDEX at an Operand Position
This new built-in function also has a friend: LINE_EXISTS. Say that you want to see
if an internal table already has an entr y for the monster at hand. If it does, then
120