This seems somewhat similar to the first question I asked on SAS L :)

In your first piece of code

%let c = %b

SAS executes the macro %b first and returns what is "left over" from the %b macro, which is the values of &i. I see this as more of a SAS trick rather than what the macro language was intended to do - although there are some old timers who may correct me on this. You therefore have advertently/inadvertently created a macro function that returns the values of a function which can then be assigned to a variable.

In the second part of the code however, you are trying again to take the output of a loop and assign it to a macro variable. However this time it is recognised as an assignment and the "%do i=1 %to &m" is seen as text, and as there are no macro quoting functions used and SAS recognises this is macro syntax it issues the error message.

I think this raises another interesting question, can SAS macro create macro code that is executable at a later time? As far as I know, Lisp allows macro code to create macro code ad infinitum. I don't think SAS does allow this, but I would be happy to be proven wrong on this. An example:

%let c = %superq(%put 1;); %unquote(c);

2009/1/16 he.terry@gmail.com <he.terry@gmail.com>: > I have two programs. One is right and the other is wrong. I am not > sure about the reason. > > The right code is as follow: > > options symbolgen mprint; > %let m=2; > %macro b; > %do i = 1 %to &m; > &i > %end; > %mend b; > > %let c = %b > ; > > > %macro a; > %put &c; > %mend a; > %a; > > The wrong code is as follow: > options symbolgen mprint; > %let m=2; > %let c = %do i = 1 %to &m; > &i > %end; > ; > > > %macro a; > %put &c; > %mend a; > %a; >