Calculations With Macro Variables

* How to do arithmetic with macro variables.
* Posted to SPSSX-L on 1999/09/24 by Rolf Kjoeller <rolf.kjoeller@GET2NET.DK>.

/* The question was:
Is it possible to perform calculations on macro variables ?
Eg. I would like to have a macro which reads a macro variable Year, but
given Year I would like to calculate the year '15 years before Year'. */.


*** Method 1.
define !subtrct (year=!tokens(1) /minus=!tokens(1)) .
preserve .
set printback=on mprint=on errors = off .

/******** BEGIN INTERESTING PART ***
!let !x = !length(!concat(!blanks(!minus)," "))
!let !newyear = !length(!substr(!blanks(!year),!x)) .
/******** END INTERESTING PART ***

compute tst = !newyear .
restore .
!enddefine .

!subtrct year=1999 minus=15 .
!subtrct year=1984 minus=25 .
/* WATCH OUT.
!subtrct year=1999 minus=2000 .

*** Method 2.
define !sub2 (year=!tokens(1) /minus=!tokens(1)) .
COMPUTE tst=!year-!minus.
EXE.
!enddefine.


!sub2 year=1999 minus=15 .
!sub2 year=1984 minus=25 .
/* WATCH OUT.
!sub2 year=1999 minus=2000 .