macro help!

[Former Member]

I have searched the sdn about the macro ,but i have found nothing valuable information. so i have to post a message for help again. the situation is :

DEFINE assign_comp.

fld = &2.

translate fld to upper case.

assign component fld of structure &1 to &3.

END-OF-DEFINITION.

FIELD-SYMBOLS:<zmst_rec> TYPE any,

<int_table> TYPE SORTED TABLE,

<tmp_table> TYPE SORTED TABLE.

FIELD-SYMBOLS:<fs>,<fs_1>.

SELECT * FROM ( ) INTO TABLE <tmp_table> .

LOOP AT <tmp_table> INTO <zmst_rec>.

assign_comp <zmst_rec>:dateto <fs_1>,datefrom <fs_2>.

ENDLOOP.

My doubt is the macro defined 3 parameters ,but the way which is assigned ....i can't understand. why use a colon,and does it mean pass dateto to datefrom ? and anybody can tell me the reason, thanks much.

[Clemenss]

Hi junchuan,

my first recommendation is not to use macros. Yo can not debug them and they decrease heavily the readability of code. Macros replace the source code at compile-time.

The second ist: Please post code using the above <_> code markup to enhance readability.

And then the colon: This is SAP BASICS. Using a colon after a statement will repeat the statement for all elements in the comma-separeated list behind.

assign_comp <zmst_rec>:dateto <fs_1>,datefrom <fs_2>.

is equal to

assign_comp <zmst_rec> dateto <fs_1>.
assign_comp <zmst_rec> datefrom <fs_2>.

A necessary precondition is that datefrom and dateto are char variables containing the strings 'DATEFROM' and 'DATETO'. Otherwise this will not work.

The macro

DEFINE assign_comp.
fld = &2.
translate fld to upper case.
assign component fld of structure &1 to &3.
END-OF-DEFINITION.

going through the compile-time macro substitution will create

translate dateto to upper case."which makes no sense at all in your case
assign component dateto of structure  <zmst_rec> to  <fs_1>.
translate datefrom to upper case."which makes no sense at all in your case
assign component datefrom of structure  <zmst_rec> to  <fs_2>.

Just to have maximum transparency, I would probably write

ASSIGN COMPONENT:
  'DATETO'    OF STRUCTURE <zmst_rec> to <fs_1>,
  'DATEFROM'  OF STRUCTURE <zmst_rec> to <fs_2>.

Less is more.

Regards,

Clemens

[Former Member]

thanks Clemens .i understand now thanks a lot.