operator: pop-float

        pop-float ket
        pops the trailing float in the given ket to the coefficient
        if the starting ket has a coefficient then multiply it by this value
        if the trailing value is not a float, then leave the ket unchanged

        pop-float |3.2>
            3.2| >
        -- coefficient of 5, so multiply by 7:
        pop-float 5|7>
            35| >
        pop-float |x: 2>
        -- again, multiply the coefficient by the value
        pop-float 5.1|x: y: 2>
            10.2|x: y>
        -- y is not a float, so leave |x: y> unchanged
        pop-float |x: y>
            |x: y>

    see also:
        push-float, to-value, to-category