Hello, can freefem + + use spline interpolation？ 
with gsl
Thank you for your reply. Is there an example of freefem + + for spline interpolation?
Yes, the example code for gsl is here gsl.edp, it has some examples for usage of splines.
Hello, do you have to build your own finite element space when this spline interpolation is used in FreeFem++? Take Lagrange interpolation as an example to define the finite element space, feaspace Wh (Th, P2). How to define this spline?