Missing math functions

[Dirk Laurie <dirk.laurie@...>]

There's no math.asinh, math.acosh, math.atanh.

The reason presumably being that ANSI C does not provide
them.

But if your C compiler provides it, you may find the included
file useful.

/* invhyp.c  (c) Dirk Laurie 2013  MIT license like Lua
 * compile on Linux with
 *   cc -shared invhyp.c -o invhyp.so
 * Then
 *   lua -l invhyp
 * gives you a math library with asinh, acosh, atanh
 */
  

#include "lua.h"
#include "lauxlib.h"
#include "lualib.h"
#include <math.h>
#include <stdio.h>

static int math_acosh (lua_State *L) {
  lua_pushnumber(L, acosh(luaL_checknumber(L, 1)));
  return 1;
}

static int math_asinh (lua_State *L) {
  double x=luaL_checknumber(L, 1);
  printf("%.16g  ->  ",x);
  x=asinh(x);
  printf("%.16g\n",x);
  lua_pushnumber(L, x);
  return 1;
}

static int math_atanh (lua_State *L) {
  lua_pushnumber(L, atanh(luaL_checknumber(L, 1)));
  return 1;
}

LUAMOD_API int luaopen_invhyp (lua_State *L) {
  lua_getglobal(L,"math");
  lua_pushstring(L,"asinh");
  lua_pushcfunction(L,math_asinh);
  lua_settable(L,-3);
  lua_pushstring(L,"acosh");
  lua_pushcfunction(L,math_acosh);
  lua_settable(L,-3);
  lua_pushstring(L,"atanh");
  lua_pushcfunction(L,math_atanh);
  lua_settable(L,-3);
  return 1;
}