Maximum

max x    max[x]

Where x is a non-symbol sortable list, returns the maximum of its items. The maximum of an atom is itself.

Nulls are ignored, except that if the items of x are all nulls, the result is negative infinity.

q)max 2 5 7 1 3
7
q)max "genie"
"n"
q)max 0N 5 0N 1 3                  / nulls are ignored
5
q)max 0N 0N                        / negative infinity if all null
-0W
q)select max price by sym from t   / use in a select statement

max is an aggregate function. It is equivalent to |/.