lmathlib文件

lua的math库是通过lua扩展而来，主要对系统math库进行了一次封装，以供lua使用，一般可以从lmathlib文件开始阅读源码。

//绝对值
static int math_abs (lua_State *L) {
  lua_pushnumber(L, l_mathop(fabs)(luaL_checknumber(L, 1)));
  return 1;
}
//正弦值
static int math_sin (lua_State *L) {
  lua_pushnumber(L, l_mathop(sin)(luaL_checknumber(L, 1)));
  return 1;
}
//双曲正弦值
static int math_sinh (lua_State *L) {
  lua_pushnumber(L, l_mathop(sinh)(luaL_checknumber(L, 1)));
  return 1;
}
//余弦值
static int math_cos (lua_State *L) {
  lua_pushnumber(L, l_mathop(cos)(luaL_checknumber(L, 1)));
  return 1;
}
//双曲余弦值
static int math_cosh (lua_State *L) {
  lua_pushnumber(L, l_mathop(cosh)(luaL_checknumber(L, 1)));
  return 1;
}
//正切值
static int math_tan (lua_State *L) {
  lua_pushnumber(L, l_mathop(tan)(luaL_checknumber(L, 1)));
  return 1;
}
//双曲正切值
static int math_tanh (lua_State *L) {
  lua_pushnumber(L, l_mathop(tanh)(luaL_checknumber(L, 1)));
  return 1;
}
//反正弦值
static int math_asin (lua_State *L) {
  lua_pushnumber(L, l_mathop(asin)(luaL_checknumber(L, 1)));
  return 1;
}
//反余弦值
static int math_acos (lua_State *L) {
  lua_pushnumber(L, l_mathop(acos)(luaL_checknumber(L, 1)));
  return 1;
}
//反正切值
static int math_atan (lua_State *L) {
  lua_pushnumber(L, l_mathop(atan)(luaL_checknumber(L, 1)));
  return 1;
}
//X-Y平面上所对应的(x,y)坐标的角度
static int math_atan2 (lua_State *L) {
  lua_pushnumber(L, l_mathop(atan2)(luaL_checknumber(L, 1),
                                luaL_checknumber(L, 2)));
  return 1;
}
//向上取整，即取不小于x的最小整数
static int math_ceil (lua_State *L) {
  lua_pushnumber(L, l_mathop(ceil)(luaL_checknumber(L, 1)));
  return 1;
}
//向下取整,即取不大于x的最大整数
static int math_floor (lua_State *L) {
  lua_pushnumber(L, l_mathop(floor)(luaL_checknumber(L, 1)));
  return 1;
}
//计算x/y的余数
static int math_fmod (lua_State *L) {
  lua_pushnumber(L, l_mathop(fmod)(luaL_checknumber(L, 1),
                               luaL_checknumber(L, 2)));
  return 1;
}
//分解x，以得到x的整数和小数部分
static int math_modf (lua_State *L) {
  lua_Number ip;
  lua_Number fp = l_mathop(modf)(luaL_checknumber(L, 1), &ip);
  lua_pushnumber(L, ip);
  lua_pushnumber(L, fp);
  return 2;
}
//计算平方根
static int math_sqrt (lua_State *L) {
  lua_pushnumber(L, l_mathop(sqrt)(luaL_checknumber(L, 1)));
  return 1;
}
//计算x的y次幂
static int math_pow (lua_State *L) {
  lua_Number x = luaL_checknumber(L, 1);
  lua_Number y = luaL_checknumber(L, 2);
  lua_pushnumber(L, l_mathop(pow)(x, y));
  return 1;
}
//计算指数幂
static int math_log (lua_State *L) {
  lua_Number x = luaL_checknumber(L, 1);
  lua_Number res;
  if (lua_isnoneornil(L, 2))
    res = l_mathop(log)(x);
  else {
    lua_Number base = luaL_checknumber(L, 2);
    if (base == (lua_Number)10.0) res = l_mathop(log10)(x);
    else res = l_mathop(log)(x)/l_mathop(log)(base);
  }
  lua_pushnumber(L, res);
  return 1;
}

#if defined(LUA_COMPAT_LOG10)
static int math_log10 (lua_State *L) {
  lua_pushnumber(L, l_mathop(log10)(luaL_checknumber(L, 1)));
  return 1;
}
#endif
//以自然常数e为底的指数函数
static int math_exp (lua_State *L) {
  lua_pushnumber(L, l_mathop(exp)(luaL_checknumber(L, 1)));
  return 1;
}
//将弧度转换为角度
static int math_deg (lua_State *L) {
  lua_pushnumber(L, luaL_checknumber(L, 1)/RADIANS_PER_DEGREE);
  return 1;
}
//将角度转换为弧度
static int math_rad (lua_State *L) {
  lua_pushnumber(L, luaL_checknumber(L, 1)*RADIANS_PER_DEGREE);
  return 1;
}
//把一个浮点数分解为尾数和指数
static int math_frexp (lua_State *L) {
  int e;
  lua_pushnumber(L, l_mathop(frexp)(luaL_checknumber(L, 1), &e));
  lua_pushinteger(L, e);
  return 2;
}
//计算value乘以2的exp次幂
static int math_ldexp (lua_State *L) {
  lua_Number x = luaL_checknumber(L, 1);
  int ep = luaL_checkint(L, 2);
  lua_pushnumber(L, l_mathop(ldexp)(x, ep));
  return 1;
}


//求最小值
static int math_min (lua_State *L) {
  int n = lua_gettop(L);  /* number of arguments */
  lua_Number dmin = luaL_checknumber(L, 1);
  int i;
  for (i=2; i<=n; i++) {
    lua_Number d = luaL_checknumber(L, i);
    if (d < dmin)
      dmin = d;
  }
  lua_pushnumber(L, dmin);
  return 1;
}

//求最大值
static int math_max (lua_State *L) {
  int n = lua_gettop(L);  /* number of arguments */
  lua_Number dmax = luaL_checknumber(L, 1);
  int i;
  for (i=2; i<=n; i++) {
    lua_Number d = luaL_checknumber(L, i);
    if (d > dmax)
      dmax = d;
  }
  lua_pushnumber(L, dmax);
  return 1;
}

//随机数
static int math_random (lua_State *L) {
  /* the `%' avoids the (rare) case of r==1, and is needed also because on
     some systems (SunOS!) `rand()' may return a value larger than RAND_MAX */
  lua_Number r = (lua_Number)(rand()%RAND_MAX) / (lua_Number)RAND_MAX;
  switch (lua_gettop(L)) {  /* check number of arguments */
    case 0: {  /* no arguments */
      lua_pushnumber(L, r);  /* Number between 0 and 1 */
      break;
    }
    case 1: {  /* only upper limit */
      lua_Number u = luaL_checknumber(L, 1);
      luaL_argcheck(L, (lua_Number)1.0 <= u, 1, "interval is empty");
      lua_pushnumber(L, l_mathop(floor)(r*u) + (lua_Number)(1.0));  /* [1, u] */
      break;
    }
    case 2: {  /* lower and upper limits */
      lua_Number l = luaL_checknumber(L, 1);
      lua_Number u = luaL_checknumber(L, 2);
      luaL_argcheck(L, l <= u, 2, "interval is empty");
      lua_pushnumber(L, l_mathop(floor)(r*(u-l+1)) + l);  /* [l, u] */
      break;
    }
    default: return luaL_error(L, "wrong number of arguments");
  }
  return 1;
}

//设置随机种子
static int math_randomseed (lua_State *L) {
  srand(luaL_checkunsigned(L, 1));
  (void)rand(); /* discard first value to avoid undesirable correlations */
  return 0;
}