ABAP REDUCE關鍵字的一些實際用途

... REDUCE type(

     INIT result = start_value

          ...

     FOR for_exp1

     FOR for_exp2

     ...

     NEXT ...

          result = iterated_value

          ... ) ...

While VALUE and NEW expressions can include FOR expressions, REDUCE must include at  

least one FOR expression. You can use all kinds of FOR expressions in REDUCE:

with IN for iterating internal tables

with UNTIL or WHILE for conditional iterations.

REPORT ZREDUCE.

DATA itab TYPE STANDARD TABLE OF i WITH EMPTY KEY.

" will generate an internal table with value 1 ~ 100

itab = VALUE #( FOR j = 1 WHILE j <= 100 ( j ) ).

DATA(sum) = REDUCE i( INIT x = 0 FOR wa IN itab NEXT x = x + wa ).

CLEAR: itab.

itab = VALUE #( FOR j = 1 THEN j + 10 WHILE j <= 100 ( j ) ).

* 1,11,21,31 ... 91

* First, the table is filled with VALUE and FOR and then it is reduced with REDUCE

* to the sum of its contents. Note that there is no THEN used to construct the table.

* If THEN is not specified explicitly, implicitly THEN j = j + 1 is used. Be also

* aware, that you can place any expression behind THEN, including method calls.

* You only have to make sure that the end condition is reached within maximal

* program run time.

DATA(result) =

 REDUCE string( INIT text = `Count up:`

                FOR n = 1 UNTIL n > 10

                NEXT text = text && | { n }| ).

" Count up: 1 2 3 4 5 6 7 8 9 10

BREAK-POINT.

TYPES outref TYPE REF TO if_demo_output.

DATA(output) =

 REDUCE outref( INIT out11  = cl_demo_output=>new( )

                     text = `Count up:`

                FOR n = 1 UNTIL n > 11

                NEXT out11 = out11->write( text )

                     "text = |{ n }| ).

                     " text = n ). * can also work

                     text = | 'Jerry' { n } 'end' | ).

output->display( ).

* 5050:

DATA itab  TYPE STANDARD TABLE OF i WITH EMPTY  KEY.

itab = VALUE #( FOR j  = 1 WHILE j <=  100 ( j ) ).

DATA(sum) = REDUCE i( INIT x = 0 FOR wa IN itab  NEXT x = x + wa ).