AMPL implement constraint

Question

I'm trying to implement the following in AMPL:

$$ i \in [N], j \in[N] \backslash \{i\}, t \in [T] $$

I have so far written the following:

subject to Con{i in PP,t in TT, j in PP : j != i}:

but it does not feel correct, is it? I also have a question about implementing this: $$ i \neq j,t $$ in a constraint, i'm only getting one to work:

subject to {i in PP,t in TT, j in PP : j != i}:

Answer 1

This looks most like the math (and avoids checking for every $(i,j,t)$ a logical condition that depends only on $i$ and $j$):

{i in PP, j in PP diff {i}, t in TT}

Answer 2

Try the following syntax:

subject to cons {i in PP,t in TT, j in PP : j diff i}:

Or

subject to cons {i in PP,t in TT, j in PP : j<>i}: