两个在ABAP里面做递归(recursion)的例子

例1.求一个节点下面所有节点的某一字段之和

*&---------------------------------------------------------------------*
*& Report  Z_BARRY_RECURSION2                                          *
*&                                                                     *
*&---------------------------------------------------------------------*
*& 求一个节点下面所有节点的某一字段之和                                *
*&---------------------------------------------------------------------*

 

AA -- BBB -- DDDD

   |      |

   |      -- EEEE

   |     

   |- CCC -- FFFF

   |      |

   |      -- GGGG

   |

   |- HHH

 

REPORT  z_barry_recursion2             .

DATA: BEGIN OF itab OCCURS 0 ,
        node(10) TYPE c,
        parentnode(10) TYPE c ,
        folder TYPE c ,
        menge TYPE i,
      END OF itab.
DATA: itab2 LIKE itab OCCURS 0 WITH HEADER LINE.
DATA: total TYPE i.

 

START-OF-SELECTION.

  itab-menge = 1.
  itab-node = 'AA'.
  itab-parentnode = ''.
  itab-folder = 'X'.
  APPEND itab.
  itab-menge = 2.
  itab-node = 'BBB'.
  itab-parentnode = 'AA'.
  itab-folder = 'X'.
  APPEND itab.
  itab-node = 'CCC'.
  itab-parentnode = 'AA'.
  itab-folder = 'X'.
  APPEND itab.
  itab-node = 'HHH'.
  itab-parentnode = 'AA'.
  itab-folder = ''.
  APPEND itab.
  itab-menge = 3.
  itab-node = 'DDDD'.
  itab-parentnode = 'BBB'.
  APPEND itab.
  itab-node = 'EEEE'.
  itab-parentnode = 'BBB'.
  APPEND itab.
  itab-node = 'FFFF'.
  itab-parentnode = 'CCC'.
  APPEND itab.
  itab-node = 'GGGG'.
  itab-parentnode = 'CCC'.
  APPEND itab.

 

  PERFORM getsum USING 'AA' total.

  WRITE total .

  SKIP 2.

 

  PERFORM gettable TABLES itab2
                   USING 'AA' .
  LOOP AT itab2.
    WRITE : / itab2-node ,itab2-parentnode,itab2-menge.
  ENDLOOP.

 

*&---------------------------------------------------------------------*
*&      Form  getsum
*&---------------------------------------------------------------------*
FORM getsum USING node sum.
  LOOP AT itab WHERE parentnode = node .
    IF itab-folder = ''.
      sum = sum + itab-menge .
    ENDIF.
    PERFORM getsum USING itab-node sum.
  ENDLOOP.
ENDFORM .                   "getsum

 

*&---------------------------------------------------------------------*
*&      Form  gettable
*&---------------------------------------------------------------------*
FORM gettable TABLES outtab
              USING node .
  LOOP AT itab WHERE parentnode = node.
    IF itab-folder = ''.
      APPEND itab TO outtab.
    ENDIF.
    PERFORM gettable TABLES outtab USING itab-node.
  ENDLOOP.
ENDFORM.                    "gettable

 

 

例2.求一个日期的前N个月的日期

REPORT  z_barry_recursion   .

DATA: old_date LIKE sy-datum ,
      new_date LIKE sy-datum ,
      back TYPE numc3 .

 

old_date = '20080417'.
back = 6.

 

PERFORM back_months USING old_date back
                    CHANGING new_date.

WRITE new_date.

*&---------------------------------------------------------------------*
*&      Form  GET_BOM
*&---------------------------------------------------------------------*
FORM back_months USING value(currdate) value(backmonths)
                 CHANGING newdate.
  DATA: year(4)    TYPE c,
        tmonths TYPE numc3,
        t1months TYPE numc3,
        day(2)     TYPE c.

  MOVE: currdate(4) TO year,
        currdate+4(2) TO tmonths,
        currdate+6(2) TO day.

  IF tmonths <= backmonths.
    currdate(4) = currdate(4) - 1.
    currdate+4(2) = '12'.
    backmonths = backmonths - tmonths.
    PERFORM back_months USING currdate backmonths
                        CHANGING newdate.
  ELSE.
    newdate(4) = currdate(4).
    newdate+6(2) = currdate+6(2).
    newdate+4(2) = currdate+4(2) - backmonths.
  ENDIF.
ENDFORM.                    "GET_BOM