Re: [pdf-devel] pdf_function.c

[jemarch]

Hello.

   cubic spline interpolation ( 1D case ) can be done in 
   about 60 lines of C code implementing 

   double pdf_eval_spline( double x, int nsamples,
           const double y[],
           const double y1[] ) 

   void pdf_solve_spline(int nsamples, 
           const double y[], 
           double y1[] ) ;

   http://mathworld.wolfram.com/CubicSpline.html

Do a general formula to solve m-dimensional cubic splines exist?
Something like that (the link talks about multi-linear interpolation):
http://kanushu.uwaterloo.ca/~tveldhui/papers/MAScThesis/node32.html

If that helps, there is an implementation of multidimensional cubic
splines in Octave 2.9.3 (written in octave). I dont know the approach
used to implement it.

It is the `interpn' octave function
(http://www.gnu.org/software/octave/doc/interpreter/Multi_002ddimensional-Interpolation.html).
 You
can find the implementation in the
/home/jemarch/tmp/octave-2.9.13/scripts/polynomial/ directory.

   I have finished an implementation of type 2 functions.

Many thanks!

BTW: are you using the `pdf_stm_peek' function? In the process of
writing the lexer I rewrote the file backend to achieve more
efficiency managing single characters. I removed the `pdf_stm_peek'
function ("peek an arbitrary large string from the stream") from the
API and added a new one: `pdf_stm_peek_char' ("peek a single character
from the stream"). The later is immediately useful in the lexer while
the first hurts the performance of char-oriented input/output.