String conctenation/merge using FOR loop inside REDUCE

[Nitish2027]

Hi Experts,

I recently came across a similar question in the forum and wanted to build a logic for it using REDUCE and FOR.

I tried many things but I have a few doubts that I would like to get your opinion on.

Below is the code with comments on exact requirement and doubts as well.

**********************************************************************
    " To merge two strings as 2 characters of first and then 2 characters of second
    " and then again 2 characters of first string and so on, until the end of both the strings.
    " Examples: str1 = 'first', str2 = 'second' then result = 'fiserscotnd'.
    "           str1 = 'home', str2 = 'book' then result = 'hobomeok'.
    "           str1 = 'hello', str2 = 'darkness' then result = 'hedallrkoness'.
    "           str1 = 'super', str2 = 'star' then result = 'sustpearr'.


    DATA: p1 TYPE string VALUE 'home',
          p2 TYPE string VALUE 'book'.

    DATA(lv_len1) = strlen( p1 ).
    DATA(lv_len2) = strlen( p2 ).
    DATA(lv_len) = lv_len1 + lv_len2.

    "Expected Result is hobomeok for this case.

**********************************************************************
    " I have many doubts in case of FOR inside REDUCE. I tried this as my first try.
    " But I think here text1 if going through the complete FOR loop and the text2 is starting to
    " fill only after text1 has already stored the value 'home' by iterating through FOR twice
    " as the length is 4 chars. So when at last text gets filled, it gives the result 'homebook'.

    DATA(result1) = REDUCE string( INIT text = ``
                                       text1 = ``
                                       text2 = ``
                      FOR i = 0 THEN i + 2 WHILE i <= lv_len
                      NEXT text1 = COND #( WHEN i < lv_len1
                                          THEN text1 && substring( val = p1 off = i len = 2 )
                                          ELSE text1 )
                           text2 = COND #( WHEN i < lv_len2
                                          THEN text2 && substring( val = p2 off = i len = 2 )
                                          ELSE text2 )
                           text = text1 && text2
                                          ).
    out->write( result1 ). "homebook

**********************************************************************.
    " In my second try I get the correct result, but this works only when both the strings
    " are of same length. Because if one string has bigger length than the other, it creates
    " a runtime error as the offset in the substring function becomes higher than the length
    " of the shorter string.

    DATA(result2) = REDUCE string( INIT text = ``
                      FOR i = 0 THEN i + 2 WHILE i <= lv_len
                      NEXT text = COND #( WHEN i < lv_len1 AND i < lv_len2
                                          THEN text && substring( val = p1 off = i len = 2 )
                                                    && substring( val = p2 off = i len = 2 )
                                          ELSE text )
                                          ).
    out->write( result2 ). "hobomeok

**********************************************************************
    " In my third try I thought of managing the length of each string individually to remove
    " the run time error. But then in this case it always takes the first when and gives the
    " value stored in the first string only.

    DATA(result3) = REDUCE string( INIT text = ``
                      FOR i = 0 THEN i + 2 WHILE i <= lv_len
                      NEXT text = COND #( WHEN i < lv_len1
                                          THEN text && substring( val = p1 off = i len = 2 )
                                          WHEN i < lv_len2
                                          THEN text && substring( val = p2 off = i len = 2 )
                                          ELSE text )
                                          ).
    out->write( result3 ). "home

**********************************************************************
    " I know I'm close but just unable to figure this out. I think I should be able to do
    " this by using REDUCE and FOR.

**********************************************************************

It would be great if someone can guide me with some suggestion where I'm going wrong and I would try to implement the new logic.

Thanks 🙂

[Sandra_Rossi]

You should first write the algorithm on "paper" and play it. It will be much easier after that.