[OSM-talk] address interpolation

Peter Körner osm-lists at mazdermind.de
Fri Oct 2 09:26:11 BST 2009


> The problem is as follows:
> 
> You see an interpolation "25a to 25c". How do you know that this means
> "25a, 25b, 25c"? You know by removing the number and then starting with
> the "a" go through code points adding one until you reach "c". Easy.
> This will work for all alphabets where that are layed out in alphabetical
> order in Unicode, and they probably all are. (but thats an assumption on
> my part :-)
> 
> But, when you see an interpolation "25 to 25c". How do you know that this
> means "25, 25a, 25b, 25c"? You again remove the number. That gives you the
> first entry. But what happens then? 
You count to the end of this interpolation-way (there are 4 nodes in, 1 
is the start and 1 is the end, so 2 in between) and substract this 
number (2) from the last char (c). Following your assumptions from above 
this should work (when you can add 1 to go to the next char, you can 
also subtract 1 to go to the previous). This way you'll first get b and 
then a - those are the chars for your houses.

Peter




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