```
@objective (m,Min,sum (LS [i, j]*C[i, j] for i, j ∈ 1:f))
```

How to make this expression read the `for i,j`

. The way I did the error appears:

syntax: invalid iteration specification

```
@objective (m,Min,sum (LS [i, j]*C[i, j] for i, j ∈ 1:f))
```

How to make this expression read the `for i,j`

. The way I did the error appears:

syntax: invalid iteration specification

You shouldn’t have spaces between a function name and the parenthesis or between the variable name and the bracket. I would have expected an `ERROR: syntax: space before "[" not allowed`

type of message instead of the iteration message, but I would fix those and see if that gets you there or closer.

Like this:

```
@objective (m,Min, sum(LS[i, j]*C[i, j] for i, j ∈ 1:f))
```

EDIT: Also, you have two loop variables (`i, j`

), but are iterating only over one dimension, that’s the source of the iteration error.

I removed the spaces, thanks.

I’m learning how to code, I don’t know how I can iterate two loop variables.

Learning is great! That’s why I’m here too. Keep asking questions.

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There are some examples here: https://docs.julialang.org/en/v1/manual/arrays/#Generator-Expressions-1

1 Like

Thanks!!!