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Re: How can I test for an open subpath ?

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On 2016-08-25, Carlos <angus@quovadis.com.ar> wrote:
> On 25/08/2016 11:42, Peter Billam wrote:
>> but I'd like to start a procedure with a lineto if there's
>> a currently open subpath, and with a moveto if there isn't.
>> Is there a neat way of doing this ?
>> Do I have to do forsenics inside pathforall ?
> It's actually quite simple using pathforall, since one of
> the procs it takes is called specifically on closepath.
> /isclosed {
>      false
>      { pop pop false exch pop }
>      { pop pop false exch pop }
>      { pop pop pop pop pop pop false exch pop }
>      { true exch pop } pathforall
> } def

Yes, that's neat.  For my use-case I changed the inital false to
true, so that with no current path it would return the same as
after a subpath has been closed, and then I took the liberty
of inverting all the booleans and renaming it is_open_subpath

/is_open_subpath {   % Carlos comp.lang.postscript 20160826 inverted
  false  % except I treat no-currentpath the same as no-open-subpath
  { pop pop true exch pop }
  { pop pop true exch pop }
  { pop pop pop pop pop pop true exch pop }
  { false exch pop } pathforall
} bind def

in which form it appears in
 http://www.pjb.com.au/comp/line_drawing.html#points2curve
 http://www.pjb.com.au/comp/free/line_drawing.ps.txt
 https://github.com/peterbillam/postscriptlib/blob/master/line_drawing.ps
and seems to work well :-) It seems sad to loop through the entire
path just in order to read the last item, but it's only once per
invocation. I'll roll it into other path-segment-constructor procs :-)

Thanks !
Peter

-- 

Peter Billam    www.pjb.com.au    www.pjb.com.au/comp/contact.html

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Thread

How can I test for an open subpath ? Peter Billam <peter@www.pjb.com.au> - 2016-08-25 09:42 +0000
  Re: How can I test for an open subpath ? Carlos <angus@quovadis.com.ar> - 2016-08-25 16:49 +0200
    Re: How can I test for an open subpath ? Peter Billam <peter@www.pjb.com.au> - 2016-08-27 04:28 +0000
    Re: How can I test for an open subpath ? jdaw1 <jdawiseman@gmail.com> - 2016-08-27 10:32 -0700

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