[geos-devel] CAPI GEOSUnionCascaded

Howard Butler howard at hobu.co
Thu Jul 15 11:13:13 PDT 2021

> On Jul 15, 2021, at 1:01 PM, Paul Ramsey <pramsey at cleverelephant.ca> wrote:
> Just stumbled over this old stub, 
> https://github.com/libgeos/geos/blob/main/capi/geos_ts_c.cpp#L1425
> In addition to GEOSUnaryUnion, which calls a cascaded union as required, we have this explicit hook into cascaded polygon union in the C API. It seems a little duplicative, which is not a high crime, but it also has a hidden feature: unlike UnaryUnion which calls the new NG routines in "safe sequence" (try full precision, fall back to gentle snapping, fall back to snap rounding), this CAPI GEOSUnionCascaded call uses the ClassicUnionStrategy, which is to say the *old* overlay functions and the HeuristicOverlay fallbacks (various forms of bit stripping and precision reduction). 
> Question: 
> - just remove this API end point entirely?

I would prefer noop'ing it and setting an error than removing entirely 

> - flip it over to also use NG semantics?

This is what you actually want, right? I do.

> - don't touch that you fool, it's important to have it as it is!

Users can continue to run older versions of the code at their discretion. 

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