> On 7 May 2020, at 20:28, Gerben Wierda <gerben.wie...@rna.nl> wrote: > > I have a METAPOST algorithm that splits a path at a certain time in two, does > something with both ends (not the ends where they were split) and then > rejoins them. > > In very rare cases this crashes, because the subpath doesn’t work as expected. > > firstPart := subpath (0,halfWayTime) of workingConn; > secondPart := subpath (halfWayTime,pathTimeLen) of workingConn; > > may sometimes result in something like this: > > metapost log > >> Path at line 0: > metapost log > (273,-427)..controls (259.50666666666666,-427) and > (246.01333333333335,-427) > metapost log > ..(232.52000000000001,-427) > metapost log > > metapost log > >> Path at line 0: > metapost log > (232.51999999999998,-427)..controls > (161.68000000000001,-427) and (90.840000000 > metapost log > 000003,-427) > metapost log > ..(20,-427) > > As can be seen in these (rare) cases the two calls to subpath result in a > different point resulting from both. so, when I later try to rejoin them with > & it fails: > > metapost log > ! Paths don't touch; '&' will be changed to '..'. > metapost log > <to be read again> > > Which means subpath doesn’t always exactly do what I expect it to do (and > many explanations, but not the official manual) state. Again, this is rare. > > I’ve done this to work around it but I wondered if there was a better > (reliable) solution > > save cutFirstPart; path cutFirstPart; cutFirstPart := firstPart > maxcutbefore fromPicOutline; > save cutSecondPart; path cutSecondPart; cutSecondPart := secondPart > maxcutafter toPicOutline; > if ((xpart point 0 of cutSecondPart) <> (xpart point infinity of > cutFirstPart)) > or ((ypart point 0 of cutSecondPart) <> (ypart point infinity of > cutFirstPart)): > resultConn := cutFirstPart--cutSecondPart; > else: > resultConn := cutFirstPart & cutSecondPart; > fi
A crude test of path pb; pb:=(5.5cm,0cm)--(5.5cm,0cm)--(10.5cm,0cm); draw pb; gives no errors so why not just join using -- all the time and save the test? -- Bruce Horrocks Hampshire, UK ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___________________________________________________________________________________
