infix operators, type 2: //

 // :
    description:
        ket1 // ket2
        divide the value of ket1 by the value of ket2
        we do our best to preserve categories
        if one ket has a category, and the other doesn't then the result has that category
        if ket1 and ket2 have different categories then return the empty ket |>
        if ket1 and ket2 are 2D, then divide them component-wise

    examples:
        |3> // |5>
            |0.6>

        |number: 3> // |5>
            |number: 0.6>

        |number: 3> // |page: 5>
            |>

        |2: 5> // |3: 7>
            |0.66667: 0.71429>

    see also:
        arithmetic, ++ , -- , ** , %% , ^^