Lines vs Polylines
Mats Elfström
A comment on the current thread on the beginning and end points of lines and polylines.
It seems as if the distinction between lines and polylines eludes users and often causes problems.
Add to that the possibility of an object with multiple segments.
Still, obtaining the beginning and end coordinates of a line object must be regarded as such a basic task that these different flavors of line objects should be dealt with inside the ObjectGeography function, instead of having the user first determine line type and then traverse all nodes and segments in order to reach the end.
I mean, how often do you really want to locate the Nth node of the Nth segment of any line.
What is the logical reason for treating line objects with two or three nodes as unrelated species?
I'm of the curious kind and seldom content with the answer "That's how it is - get used to it" when I trip over a seemingly unnecessary obstacle.
Comments are welcome.
Regards, Mats.E
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Mats Elfström, Väpplingvägen 21, SE-227 38 LUND, Sweden
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Uffe Kousgaard
The reason is lines and polylines are stored differently inside the TAB file (a line is more compact than a polyline with 2 nodes). And lines can not be smoothed.
But I agree, the mapbasic API should be the same for both object types.
For the same reason my ToolBox (http://www.routeware.dk/toolbox.php) contains a function for swapping between lines and polylines (not listed on the website, but it's in there!). If you change to polylines, mapbasic programming gets easier. If you change to lines, the TAB file gets more compact.
Kind regards
Uffe Kousgaard
Mats Elfström wrote:
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Thomas Bacon
I have to agree with Mats on this. Surely one would assume that the function in question would apply to both types of line objects. The ObjectInfo function to select the Nth node of the Nth segment could still apply for those cases where it may be needed.
It seems every time I work with polyline datasets I have to use this convoluted method to determine the beginning/end coordinates of an object (and I’ve usually forgotten that ObjectGeography doesn’t work, so it ends up becoming even more of a pain!).
To anyone at MI; is there a good reason why the functions are designed like this? Any possibility of this being improved in future releases?
Regards,
Tom
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Mats Elfström
The reason remains to be revealed.
Mats.E