Error in defining a symbolic link

New to AMPL
1

I passed my code through chat-gpt and was told the code should work, but when I try to load my model, I get an error:

line 1 (offset 9):
        syntax error
context:  set grid  >>> symbolic; <<<

I explained the error to chat-gpt and was told I might have unprintable characters so I ran cat -A on my input file to get:

set grid symbolic;
set beam in b_supply symbolic;
set beam_options{i in grid} within beam:=beam;
param b_supply{beam} >= 0;
param g_demand{grid} >= 0;
param g_b_bps{grid,beam};
var g_assign{i in grid, j in beam_options} binary;
minimize Aggregate:
    sum({i in grid, j in beam_options} min(0,g_demand[i]/g_b_bps[i,j] - g_assign[i,j]*g_demand[i]/g_b_bps[i,j])) + 
    sum({i in grid, j in beam} g_assign[i,j]*g_demand[i]/g_b_bps[i,j]);
subject to card(g_assign, beam_options) <= 1;
subject to sum({i in grid, j in beam_options} g_assign[i,j]*g_demand[i]/g_b_bps[i,j]) <= b_supply[j];

I checked to see if grid was a reserved word and I did not find it on the list. symbolic is a reserved word but I think I am using it correctly.

I am running ampl version: AMPL Version 20240606 (MSVC 19.40.33811.0, 64-bit) which I include because chat-gpt also asked this question.

2

symbolic is only a property of parameters: normally, a parameter only takes numerical values, but if it is defined as symbolic then it takes character-string values instead.

Any set can contain numerical or string values (or even some numerical values and some string values), so there is no need to define a set as symbolic. That’s why a definition like set grid symbolic; is rejected as an error; instead, you should just define set grid;.