Hey guys,

I´m currently working on optimization model for my master thesis.

after the first compile i was able to fix some errors. However, I do not know how to deal with the following problem:

In my model I use some running parameters to describe planes in the 2 dimensional space. With an specific origin, the plane is supposed to spread out in x and y dimension.

therefore, I have developed this snipped of code:

```
sum(x,
sum(y,
sum(aa$(ord(aa) <= Start_Mach_Hor(m)),
sum(bb$(ord(bb)<=Start_Mach_Vert(m)),
Start_Mach_Pos(x,y,m)*Occ_Fac(k,x+aa-1,y+bb-1)
)
)
)
)
```

I aimed to use the alias sets aa for x and bb for y to describe the plane (in specific, this part tests whether the point (x+aa-1,y+bb-1) is occupied by the plane, if the bottom left corner is located at (x,y)); if you need more context, let me know.

Apparently it is not allowed, to have more than one set in the subset of the parameter Occ_Fac… What other options do I have to model this type of issue in GAMS?

Error Messages

```
8 ')' expected
133 Incompatible operands for addition
147 Real value for lag operator expected
148 Dimension different - The symbol is referenced with more/less
indices as declared
201 Invalid argument for function
408 Too many ),] or }
409 Unrecognizable item - skip to find a new statement
looking for a ';' or a key word to get started again
```

I would be grateful for any kind of ideas and input.

Best,

Patrick