I really appreciate the addition of tanh into core postgres.
If someone doubts it is useful: it is used as a part of math in geographical calculations.
Say you have your cars in planar Mercator projection and want to move them "1 second forward by this heading with this speed". sin/cos and the distance on X/Y, but the distance must be scaled properly - and that scaling coefficient is cosd(latitude), which you don't have directly - you have it in projected meters. If you don't want to fire up full-featured PostGIS on this hot path you inline all formulas together, result is nice and small - but has tanh in it, which I was surprised to find only in Oracle Compatibility extensions. Pure sql tanh was good enough, but gave me disturbance :)
Le mar. 12 mars 2019 à 20:57, Tom Lane <tgl@sss.pgh.pa.us> a écrit :
Lætitia Avrot <laetitia.avrot@gmail.com> writes: > So, as you're asking that too, maybe my reasons weren't good enough. You'll > find enclosed a new version of the patch > with asinh, acosh and atanh (v5).
Pushed with some minor adjustments (mainly cleanup of the error handling).
> Then I tried for several days to implement the 6 last hyperbolic functions, > but I wasn't satisfied with the result, so I just dropped it.
Yeah, I agree that sech() and so on are not worth the trouble. If they were commonly used, they'd be in POSIX ...
