RE: HP48-HP50G : Error functions ERF(z), FRESNEL integrals, PROBIT, etc.

[LdBeth]

I have written ERF and iERF for real numbers in SysRPL using Sergei Winitzki's A handy approximation for the error function and its inverse which I believe the inverse erf function is as good as the UserRPL version posted here, and is much faster.

I have originally planned to use that to computing Q function and inverse Q function, but the accuracy is only as good as 3-4 digits after decimal point even with extended real been used, so I decided to give up until I figure out a cheap way to compute the function using Taylor series.

You may find the binary for HP50g (and I believed should be compatible with HP49g at least), with the source code

https://github.com/LdBeth/eflib/releases/tag/v0.9.0