AMPL does not have a syntax like that; you have to write

set A;
set B;
set C;

The same is true of parameters and variables. It is rare that an AMPL model has a very large number of sets, however; also it is rare to have many simple definitions like paramp; or varx; without any indexing expressions, bounds, or other qualifications.

Can you give an example of a model that you would like to write, where setA,B,C; or paramp1,p2,p3; would be very helpful? Maybe there is a better way to do it that would not involve so much typing.

AMPL does not have a syntax like that; you have to write

set A;
set B;
set C;

The same is true of parameters and variables. It is rare that an AMPL model has a very large number of sets, however; also it is rare to have many simple definitions like “param p;” or “var x;” without any indexing expressions, bounds, or other qualifications.

Can you give an example of a model that you would like to write, where “set A; set B; set C;” or “param p1; param p2; param p3;” would be very helpful? Maybe there is a better way to do it that would not involve so much typing.