Date:         Thu, 25 Jul 2002 15:57:43 -0500
Reply-To:     goldbergj@MSNOTES.WUSTL.EDU
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         goldbergj@MSNOTES.WUSTL.EDU
Subject:      Re: Double Assignment
Content-type: text/plain; charset=us-ascii

Aha!  Because of the implied "and"!

Jonathan Goldberg
Missouri Alcoholism Research Center
Washington University School of Medicine
40 N. Kingshighway, Suite One
St. Louis, MO 63108
314-286-2212

----- Forwarded by Jonathan Goldberg/MARC/Psychiatry/Medicine/Washington
University on 07/25/02 04:17 PM -----

                      Jonathan Goldberg
                                               To:       SAS-L
                      07/25/02 03:43 PM        cc:
                                               Subject:  Re: Double Assignment




Sigurd Hermansen <HERMANS1@WESTAT.COM> says:

I would not trust a programmer who leaves out the parentheses. What rules
of
operator precedence apply in multiple assignments across the same operator?

Try to explain how SAS will evaluate
                         var1=var2=var3=7;
  to someone other than a committed (or soon to be) SAS programmer!

Try to explain it to me!  According to the documentation, = is a group 5
operator, and pairs are evaluated left to right.  If so, explain:

1          data _null_;
2            v1 = 7;
3            v2 = 7;
4            v3 = v1=v2=7; *should be 0;
5            put v3=;
6          run;

v3=1

Now, either

4            v3 = v1=(v2=7); *should be 0;  or
4            v3 = (v1=v2)=7; *should be 0;

get v3=0.

I thought I understood this;  obviously I'm overlooking something.

Jonathan Goldberg
Missouri Alcoholism Research Center
Washington University School of Medicine
40 N. Kingshighway, Suite One
St. Louis, MO 63108
314-286-2212