[pstricks] How can I make a double line with no color in between?

[Herbert Voss]

Am 24.09.2016 um 12:30 schrieb Luis Sequeira:
>>
>> It is not possible to set opacity only the inner line.
>>
>
> That is a pity.

I cannot see the sense of an opacity for the innerline
and not the outer line. However, define an inneropacity
and \tx at setInnerStrokeTransparency and modifiy the macro
\pst at doublestroke

Herbert