How to build a dynamically loaded library from this source
 ----------------------------------------------------------

Source files are included here for two plugin libraries.

demo_plugin.c provides three toy functions just for the purpose
of running the unit test / demo "plugin.dem".

uigamma_plugin.c provides an implementation of the regularized
upper incomplete gamma function Q(a,x) [NIST DLMF eq. 8.2.4].
This code is already built in to gnuplot version 5.5 and later,
but may be useful to provide this function as a plugin for earlier
gnuplot versions.

If you are configuring and building gnuplot from the top level of
the source tree then autoconf/automake will create a Makefile for
you and "make" should be sufficient to build the demo plugin.

If you are building _only_ this plugin demo, under linux a minimal
build command is

    gcc -shared -lm -fPIC -o demo_plugin.so demo_plugin.c

Under Windows + mingw it is

    gcc -shared -lm -o newprogram.dll newprogram.c

An equivalent build command should work for the uigamma plugin or
one you have created yourself.

    gcc -shared -lm -fPIC -o uigamma_plugin.so uigamma_plugin.c

Type "help import" in a gnuplot session for examples of how to
load a function from a plugin library.  The suggested sequence
of commands for uigamma is

    gnuplot> import Q(a,x) from "uigamma_plugin"
    gnuplot> uigamma(a,x) = ((x<1 || x<a) ? 1.0-igamma(a,x) : Q(a,x))

	- Ethan