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<div class="" style="word-wrap:break-word">Yes, that works very nicely (though to get a visible gap I had to use black line width 0.8 pt (I think that is the default) and white line width 4.5 pt.
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<div class="">A different but related question: is it possible to do arithmetic inside one of these macros?</div>
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<div class="">I have set it up so that the node at integer coordinates (i,j) is called Vij. Then I have two macros, one for an edge joining Vij to V(i+1)j, but can only do it by entering i, j, and i+1 by hand:</div>
<div class="">\stay{i}{i+1}{j}, defined by</div>
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<div class="">\newcommand{\stay}[3]{\ncline{V#1#3}{V#2#3}}%</div>
<div class="">%<span class="x_Apple-tab-span" style="white-space:pre"> </span>Usage: [V13,V23]: 2=1+1, and join position 3 at level 1 to itself</div>
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<div class=""> and another for two edges,one joining Vij to V(i+1)(j+1) over one joining Vi(j+1) to V(i+1)j:</div>
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<div class="">\cross{i}{i+1}{j}{j+1}(or reverse j and j+1 to get a negative crossing) defined by</div>
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<div class="">\newcommand{\cross}[4]{</div>
<div class=""><span class="x_Apple-tab-span" style="white-space:pre"></span>\ncline{V#1#4}{V#2#3}</div>
<div class=""><span class="x_Apple-tab-span" style="white-space:pre"></span>\ncline[linewidth=4.5pt, linecolor=white]{V#1#3}{V#2#4}</div>
<div class=""><span class="x_Apple-tab-span" style="white-space:pre"></span>\ncline[linewidth=0.8pt, linecolor=black]{V#1#3}{V#2#4}</div>
<div class="">}<span class="x_Apple-tab-span" style="white-space:pre"> </span>%Usage: [V13,V24] crosses over [V14,V23]--ie,2=1+1, and cross 3 to 4 (over)</div>
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<div class="">It would be convenient to get two better levels of efficiency:</div>
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<div class="">1. Redefine \stay so that only i and j need be entered, i+1 being computed from this and entered automatically;</div>
<div class="">similarly enter only i and j for cross, computing i+1 and j+1 internally;</div>
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<div class="">2. Combine these to only enter i and j, and get a crossing of [Vij,V(i+1)(j+1)] over [Vi(j+1),V(i+1)j], and “stay” for all other positions between level i and level i+1.</div>
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<div class="">For (1) I am not sure whether there is an option, and if so should I use the reverse Polish notation used by Metafont; and for (2) I don’t know if one can insert a kind of “if…then..” loop inside one of these commands.</div>
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<div class="">Any information/suggestions gratefully accepted. The current way of doing it is counterintuitive and prone to error.</div>
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<div class="">Here is the code I have presently, and the output:</div>
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<div class="">On Jun 13, 2016, at 16:18, Nitecki, Zbigniew H. <<a href="mailto:Zbigniew.Nitecki@tufts.edu" class="">Zbigniew.Nitecki@tufts.edu</a>> wrote:</div>
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<div class="" style="word-wrap:break-word">Nice idea—thanks. I’ll try it.
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<div class="">On Jun 13, 2016, at 13:43, Michael Sharpe <<a href="mailto:msharpe@ucsd.edu" class="">msharpe@ucsd.edu</a>> wrote:</div>
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<blockquote type="cite" class="">On Jun 13, 2016, at 7:02 AM, Nitecki, Zbigniew H. <<a href="mailto:Zbigniew.Nitecki@tufts.edu" class="">Zbigniew.Nitecki@tufts.edu</a>> wrote:<br class="">
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In trying to create braid diagrams, I would like (in an automatic way) to create crossings which go “over” other crossings. That is, something like the \rput* option, that is, an \ncline{A}{B} which, if it crosses an earlier \ncline{C}{D}, dominates it, in
the sense that there is a slight space around \ncline{A}{B} so that \ncline{C}{D} “breaks” at the crossing point. My first guess, \ncline* , has a totally different effect—the unstarred \ncline becomes totally invisible.<br class="">
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Is there such an option? Of course a workaround is to give \ncline{C}{D} linestyle=dashed, but the standard picture is to only have a break near the crossing, otherwise it is simply a straight line.<br class="">
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You can achieve this effect by drawing each node connection using two passes. On the first pass, draw a white curve about 2pt wider than your standard curve width, and draw the real node connection on the second pass. This can all be put into a small macro,
for efficiency.<br class="">
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