# How `+' and `-' Logic Affects Intersection Settings

The assignment of intersection quantity refers to the number of intersections of sets being sought in the search. This presumes that all sets are equal to each other in value. A search for:

```life  love  death
=life =love =death  (same as above)```

presumes that each set has equal value; if something from each set is found, it would reflect an intersection quantity of 2, as it contains 2 intersections of "equal" value. In Metamorph terms, this is referred to as "set logic".

When you assign a ``+`' ("must include") logic operator to a set, this means that you must include something from that designated set in any hit that is found. When you assign a ``-`' ("not") logic operator to a set, this means that you must exclude any hit which contains any element from that designated set.

Examples of these might be:

```+spirit =life =love =death
or
-alien =life =love =death```

It doesn't matter whether the equal sign ``=`' is entered or not. It also doesn't matter what sequence these operand sets are entered in, or how many of each. The only rule is you cannot enter only "not" sets.

In the above two examples, the maximum intersection quantity is still 2. The "must include" (`+`) set ("and logic") and the "must exclude" (`-`) set ("not logic") are outside the calculation of maximum intersections possible, as both are special cases. In a search where you designate something like this:

`war peace -Reagan +diplomacy`

the maximum intersection quantity is only 1, referring to an intersection of the "`war`" and the "`peace`" sets. Therefore, if you wish to definitely find something related to "`diplomacy`", but to exclude any references related to "`Reagan`", and you want to intersect what is found with either war or peace, set intersections to 0:

`@0 war peace -Reagan +diplomacy`

The 0 intersection setting applies to either the "`war`" set or the "`peace`" set (the unmarked equally weighted sets), as both "`Reagan`" and "`diplomacy`" are special cases and not included in the intersection quantity calculation.