Difference: LogicInAMPL (5 vs. 6)

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1. <e> in <SET> is true if <e> is a member of <SET>;

1. exists {<e> in <SET>} <expression> is true if some <e> in <SET> has <expression> being true;
2. forall {<e> in <SET>} <expression> is true if all <e> in <SET> have <expression> being true;
3. <SUBSET> within <SET> is true if all the elements in <SUBSET> are in <SET>;