PFNGLVERTEXATTRIBL4DPROC

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
extern (C)
alias PFNGLVERTEXATTRIBL4DPROC = void function(GLuint index, GLdouble x, GLdouble y, GLdouble z, GLdouble w)

Meta