Technical Articles

Brandon Caulfield

September 12, 2020 1 minute read

The ABAP REDUCE Operator | A Tutorial for 2020

On one of my more recent projects I went through a code review and afterwards my team lead pulled me aside and asked me to explain something. As it turns out he was referring to my use of the REDUCE operator in one the class methods. Much to my surprise this particular operator is not as widely used as I thought and the reason doesn’t seem to be that it’s actually hard to use but rather it just “looks” difficult to begin with.

It’s a great way to quickly and efficiently sum up or collect strings in a way that lets you summarize large tables of information. It’s also, in my humble opinion, a very clean and tidy way to collect summarised data making the logic easy to read for other developers.

So in this article I really want to encourage you, if you aren’t already doing so, to give the REDUCE operator a try 🙂

The SAP documentation on this particular operator is really well written and so I made a short video simply following 3 examples directly from the online documentation.

These are the three examples I run through:

REDUCE – Reduction Operator – https://help.sap.com/doc/abapdocu_751_index_htm/7.51/en-us/abenconstructor_expression_reduce.htm

Creating Values with FOR and REDUCE – https://help.sap.com/doc/abapdocu_751_index_htm/7.51/en-us/abencond_iteration_reduce_abexa.htm

Table Reductions, Summation of an Array – https://help.sap.com/doc/abapdocu_751_index_htm/7.51/en-us/abenreduce_simple_abexa.htm

There’s also a great blog post by Horst Keller on the subject – https://blogs.sap.com/2016/08/25/i-dont-like-reduce-i-love-it/

The example can be found in this GitHub Repo – https://github.com/brandoncaulfield/youtube-abap/blob/master/z_reduce_example.abap

If you have any questions or anything you’d like to add, please let me know in a comment and I’ll help where I can.

Thanks for reading!

6 Comments

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Jakob Marius Kjær

September 14, 2020 at 3:44 am

Great stuff Brendan, thanks for this.

I've been a "casual undercover" abap developer for about 10 years, but only recently starting to get into the more functional programming in abap. So it's to get these types of examples.

Keep going!

Brandon Caulfield

Blog Post Author

September 14, 2020 at 8:10 am

Thanks Jakob Marius Kjær! Im glad it was of some help. I’m busy with an Advanced ABAP Series on YouTube so if you have any concepts you’d like me to add just let me know!

Matthew Billingham

September 14, 2020 at 12:00 pm

I loved REDUCE so much that when I was working on a 7.31 system, I implemented it using classes/interfaces.

Brandon Caulfield

Blog Post Author

September 14, 2020 at 3:36 pm

That’s brilliant Matthew Billingham ! How did you manage that? Might be nice for anyone reading still on 7.31 or below 🙂

Matthew Billingham

September 14, 2020 at 3:43 pm

I'll see if I can dig it out...

Matthew Billingham

September 17, 2020 at 9:55 am

It's a limited reduce, but it suited the functionality I needed at the time! So I have an interface ZIF_CONVERTOR

interface ZIF_CONVERTER
  public .


  methods CONVERT
    importing
      !I_INPUT type ANY
    exporting
      value(E_OUTPUT) type CSEQUENCE .
endinterface.

And I have a static method in a utility class

METHODS:
  reduce_table
    IMPORTING
      i_input TYPE ANY TABLE	
      i_delimiter TYPE CHAR1 DEFAULT ','
      i_convertor TYPE REF TO zif_converter OPTIONAL	
    RETURNING
      VALUE( R_REDUCED ) TYPE string.	
...
  METHOD reduce_table.
    DATA line_ref TYPE REF TO data.
    CREATE DATA line_ref LIKE LINE OF i_input.
    FIELD-SYMBOLS <line> TYPE any.
    ASSIGN line_ref->* TO <line>.

    DATA text TYPE string.
    LOOP AT i_input INTO <line>.
      IF i_converter IS NOT BOUND.
        text = <line>.
      ELSE.
        i_converter->convert( EXPORTING i_input = <line> IMPORTING e_output = text ).
      ENDIF.
      AT FIRST.
        r_reduced = text.
        CONTINUE.
      ENDAT.
      r_reduced = r_reduced && i_delimiter && text.
    ENDLOOP.
  ENDMETHOD.

And you use it like this:

REPORT zreduce_demo.

CLASS lcl_make_upper DEFINITION.
  PUBLIC SECTION.
    INTERFACES zif_converter.
ENDCLASS.

CLASS lcl_make_upper IMPLEMENTATION.
  METHOD zif_converter~convert.
    e_output = to_upper( i_input ).
  ENDMETHOD.
ENDCLASS.

CLASS lcl_extract_numbers DEFINITION.
  PUBLIC SECTION.
    INTERFACES zif_converter.
ENDCLASS.

CLASS lcl_extract_numbers IMPLEMENTATION.
  METHOD zif_converter~convert.
    DATA input TYPE string.
    input = i_input.
    DO strlen( input ) TIMES.
      DATA pos TYPE syindex.
      pos = sy-index - 1.
      DATA char TYPE c LENGTH 1.
      char = substring( val = input off = pos len = 1 ).
      CHECK char CA '0123456789'.
      e_output = e_output && char.
    ENDDO.
  ENDMETHOD.
ENDCLASS.

START-OF-SELECTION.
  " Set up test data
  DATA test_data TYPE string_table.
  INSERT `String1` INTO TABLE test_data.
  INSERT `String2` INTO TABLE test_data.
  INSERT `String3` INTO TABLE test_data.
  " Instantiate the class that converts to upper case
  DATA to_upper_converter TYPE REF TO zif_converter.
  CREATE OBJECT to_upper_converter TYPE lcl_make_upper.
  " Instantiate the class that extracts numbers
  DATA get_number_converter TYPE REF TO zif_converter.
  CREATE OBJECT get_number_converter TYPE lcl_extract_numbers.
  " Output test data
  cl_demo_output=>begin_section( 'Test Data' ).
  cl_demo_output=>write_data( test_data ).
  cl_demo_output=>end_section( ).
  " Convert to upper case and reduce
  data uppered type string.
  uppered = zcl_utils=>reduce_table( i_input = test_data i_converter = to_upper_converter ).
  cl_demo_output=>begin_section( 'Converted to uppercase and reduced' ).
  cl_demo_output=>write_data( uppered ).
  cl_demo_output=>end_section( ).
  " Extract numbers and reduce
  data extracted type string.
  extracted = zcl_utils=>reduce_table( i_input = test_data i_converter = get_number_converter ).
  cl_demo_output=>begin_section( 'Numbers extracted and reduced' ).
  cl_demo_output=>write_data( extracted ).
  cl_demo_output=>end_section( ).
  " Display
  cl_demo_output=>display( ).

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The ABAP REDUCE Operator | A Tutorial for 2020

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