Re: Fast integer arithmetic

[Enrico Colombini <erix@...>]

John D. Ramsdell wrote:
> A compile option to produce Lua binaries without
> floating point instructions would create this faster version of Lua.

I just put this at the end of luaconf.h. It may not be perfect, but it 
works (some of the redefinitions are identical to the originals, I put 
them in for clarity).

Re-reading it, I'm not sure about LUAI_MAXNUMBER2STR. Should I count the 
terminator? I'll have to check.

  Enrico

-----------------------------------------------------------------

/*
 * Notes:
 * - pow() still uses double and is therefore slow
 * - string.format('%f') converts to double with decimal part = 0
 */

/* this line switches LUA_NUMBER from double to int */
#define LUA_NUMBER_INT

/* patch starts here */
#ifdef LUA_NUMBER_INT

#undef LUA_NUMBER_DOUBLE

#undef LUA_NUMBER
#define LUA_NUMBER          int

#undef  LUAI_UACNUMBER
#define LUAI_UACNUMBER	    int

#undef LUA_NUMBER_SCAN
#undef LUA_NUMBER_FMT
#undef LUAI_MAXNUMBER2STR
#undef lua_str2number
#define LUA_NUMBER_SCAN     "%d"
#define LUA_NUMBER_FMT      "%d"
#define LUAI_MAXNUMBER2STR	12 /* 10 digits, sign, point, and \0 */
#define lua_str2number(s,p)	strtol((s), (p), 10)

#undef luai_nummod
#undef luai_numpow
#define luai_nummod(a,b)    ((a) % (b))
#define luai_numpow(a,b)    (int)(pow((double)a,(double)b) + 0.5)

#undef lua_number2int
#undef lua_number2integer
#define lua_number2int(i,d) ((i)=(int)(d))
#define lua_number2integer(i,d) ((i)=(lua_Integer)(d))

#endif /*LUA_NUMBER_INT*/
/* patch ends here */