misc: |>

|>:
    description:
        |>
        the empty ket
        any time an op|ket> pair is invoked, and they are not defined, then the empty ket is returned
        any operator or function where the input doesn't make sense, the empty ket is usually returned
        it is the identity element for superposition addition: sp + |> == |> + sp == sp
        it is the identity element for ket merge: |label> _ |> == |> _ |label> == |label>
        it is the identity element for ket colon merge: |label> :_ |> == |> :_ |label> == |label>
        there is a special operator the do-you-know operator, that returns |no> if applied to the empty ket, |yes> otherwise
        sometimes used with value-if() to return a default value if the computation fails
        to remove empty kets from a sequence, use the sdrop operator
        in the context of a superposition being a list, |> is the equivalent of the empty list

    examples:
        do-you-know |>
            |no>

        do-you-know |something ...>
            |yes>

        -- the range operator:
        -- if applied to a valid range ket, then return that range, else return the ket unchanged
        range |*> #=>
            the |result> => compile (|op: range> . |> . ssplit[" .. "] |__self>)
            value-if( do-you-know the |result>, the |result>, |__self>)

        -- now apply it:
        range (|fish> . |3 .. 5> . |apples> . |books> . |2 .. 3 .. 0.25> . |house>)
            |fish> . |3> + |4> + |5> . |apples> . |books> . |2> + |2.25> + |2.5> + |2.75> + |3> . |house>

    see also:
        do-you-know, drop, sdrop, value-if