Within a procedure, the special name _nresults has as its value the number of variables on the left-hand side of the expression in which the procedure was called.  If the procedure call did not involve an assignment, then _nresults is given the value undefined.  If the procedure call is nested inside another expression, the value of _nresults is also set to `undefined`.  Any time the procedure call on the right-side of an assignment is part of an expression more complicated than a simple function call, _nresults will be set to `undefined`.

Do not use _nresults with option remember or option cache. Only the first result computed is stored in the remember table.  Subsequent results with the same input and a different value for _nresults will not respect the current value of _nresults. The Cache package can be used to manually manipulate and simulate a remember table that works with _nresults.

maxmin := proc () local max, min, i;
    max := _passed[1];
    min := _passed[1];
    for i from 2 to _npassed do
    if _passed[i] > max then
            max := _passed[i]
    elif _passed[i] < min then
            min := _passed[i]
        end if
    end do;
    if _nresults = 2 then
    max, min
    else
    max
    end if
end proc: