> On 8 May 2020, at 00:46, n...@scorecrow.com wrote: > > > >> 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?
Because the double exact points are also creating (different) problems in my algorithm as they make the path have 'no direction' at that point (direction is (0,0). G > > -- > 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 > ___________________________________________________________________________________
___________________________________________________________________________________ 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 ___________________________________________________________________________________
