Alter identifier names with macros in gams

Question

I have multiple parameters named in the same convention, e.g.

parameter
par_1_1 /1/
par_1_2 /2/
par_2_1 /3/
par_2_2 /4/
;

I want to define a macro, which will be replaced (based on the input) by the identifier, e.g.

$macro f(x) (x_1_1) 

and use it in my program, e.g.

variable x;
x.lo = -1000;
x.up = 1000;

$macro f(x) (x_1_1)

parameter
par_1_1 /1/
par_1_2 /2/
par_2_1 /3/
par_2_2 /4/
;
variable obj; equation eqobj; eqobj.. obj =e= x;
equation eqcon; eqcon.. x =l= f3(par);


model mod /all/;
solve mod minimizing obj using minlp;

Unfortunaly, this is not working because gams will consider x_1_1 as an (undefined) symbol. Is there any way to accomplish this?

Answer 1

Not sure, if I got it exactly right, what you want to do, but does this work?

variable x;
x.lo = -1000;
x.up = 1000;

$macro f(x,y) par_&x&_&y

parameter
par_1_1 /1/
par_1_2 /2/
par_2_1 /3/
par_2_2 /4/
;
variable obj; equation eqobj; eqobj.. obj =e= x;
equation eqcon; eqcon.. x =l= f(1,2);


model mod /all/;
solve mod minimizing obj using minlp;