[Bug-gsl] Re: Interpolation

[Brian Gough]

At Mon, 15 Nov 2010 22:15:08 +0300,
Евгений Курбатов wrote:
> 
> Dear Brian
> 
> I like GSL very much and I'm using it widely but..
> why the interpolating routines become extrapolating sometimes?  Today I spent 
> several hours to find the stupid bug in my program due to interpolation 
> bounds violation.  When an interpolation point becomes greater than right 
> bound or lower than left then no error returns but the routine extrapolates a 
> function value to that point giving very brave values.  Only observing of 
> sources showed this is the feature, not the bug.
> Would it be better to introduce some flags for gsl_interp_init or somewhere 
> indicating the needing for bounds check.  This check can be done in a one 
> line (e.g. line 277 of cspline.c).  Or just hardcode this checkup without a 
> flags.  Or at least note this feature in a manual.
> 

That sounds like a good idea, to just hardcode an error for values
outside the range, can you send a patch for it.  Thanks.

-- 
Brian Gough