[Bug-gsl] [bug #39713] roots/secant.c "derivative value is not finite" for a good guess

[Rhys Ulerich]

Follow-up Comment #10, bug #39713 (project gsl):

Agreed on GSL 2.0 permitting API changes.

I'm not aware of an API-breaking #define sitting anywhere.  Having seen these
employed extensively along with goofy backward-compatible macros within the
HDF5 APIs, I hate them.  An example is
http://www.hdfgroup.org/HDF5/doc/RM/RM_H5T.html#Datatype-ArrayCreate.  This is
a disgusting, disgusting thing that screws up package management (e.g. is the
hdf5 API the new or old one) which percolates into every dependent package. 
It is consequently wildly unpleasant to attempt to use HDF5 packages in
Debian-ish distros.

AFAIK, GSL 1.x is to be backwards compatible forever, including ABI as much as
possible.  Much of this sort of conversation should be had on the developer
list so others can correct me where I'm wrong.

What's the objection to having the secant solver shortcircuiting on f == 0.0
and then returning GSL_SUCCESS?  Would that solve the reported issue?  I'm
agreeable to discussing fixing or improving the solver API behavior in a
feature ticket or on the mailing list, but we're too far afield here for a bug
tracker.

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