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'x//y' extended to floats + more comments about module and floor

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division operations
This commit is contained in:
Roberto Ierusalimschy
2014-11-21 10:15:00 -02:00
parent 5d628519d3
commit 049cf14cf9
2 changed files with 43 additions and 24 deletions
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49
lvm.c
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@@ -1,5 +1,5 @@
/*
** $Id: lvm.c,v 2.228 2014/11/03 20:07:47 roberto Exp roberto $
** $Id: lvm.c,v 2.229 2014/11/19 15:05:15 roberto Exp roberto $
** Lua virtual machine
** See Copyright Notice in lua.h
*/
@@ -428,8 +428,10 @@ void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) {
/*
** Integer division; return 'm // n'. (Assume that C division with
** negative operands follows C99 behavior.)
** Integer division; return 'm // n', that is, floor(m/n).
** C division truncates its result (rounds towards zero).
** 'floor(q) == trunc(q)' when 'q >= 0' or when 'q' is integer,
** otherwise 'floor(q) == trunc(q) - 1'.
*/
lua_Integer luaV_div (lua_State *L, lua_Integer m, lua_Integer n) {
if (l_castS2U(n) + 1u <= 1u) { /* special cases: -1 or 0 */
@@ -438,18 +440,18 @@ lua_Integer luaV_div (lua_State *L, lua_Integer m, lua_Integer n) {
return intop(-, 0, m); /* n==-1; avoid overflow with 0x80000...//-1 */
}
else {
lua_Integer d = m / n; /* perform division */
if ((m ^ n) >= 0 || m % n == 0) /* same signal or no rest? */
return d;
else
return d - 1; /* correct 'div' for negative case */
lua_Integer q = m / n; /* perform C division */
if ((m ^ n) < 0 && m % n != 0) /* 'm/n' would be negative non-integer? */
q -= 1; /* correct result for different rounding */
return q;
}
}
/*
** Integer modulus; return 'm % n'. (Assume that C '%' with
** negative operands follows C99 behavior.)
** negative operands follows C99 behavior. See previous comment
** about luaV_div.)
*/
lua_Integer luaV_mod (lua_State *L, lua_Integer m, lua_Integer n) {
if (l_castS2U(n) + 1u <= 1u) { /* special cases: -1 or 0 */
@@ -459,10 +461,9 @@ lua_Integer luaV_mod (lua_State *L, lua_Integer m, lua_Integer n) {
}
else {
lua_Integer r = m % n;
if (r == 0 || (m ^ n) >= 0) /* no rest or same signal? */
return r;
else
return r + n; /* correct 'mod' for negative case */
if (r != 0 && (m ^ n) < 0) /* 'm/n' would be non-integer negative? */
r += n; /* correct result for different rounding */
return r;
}
}
@@ -778,15 +779,6 @@ void luaV_execute (lua_State *L) {
}
else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_DIV)); }
)
vmcase(OP_IDIV, /* integer division */
TValue *rb = RKB(i);
TValue *rc = RKC(i);
lua_Integer ib; lua_Integer ic;
if (tointeger(rb, &ib) && tointeger(rc, &ic)) {
setivalue(ra, luaV_div(L, ib, ic));
}
else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_IDIV)); }
)
vmcase(OP_BAND,
TValue *rb = RKB(i);
TValue *rc = RKC(i);
@@ -847,6 +839,19 @@ void luaV_execute (lua_State *L) {
}
else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_MOD)); }
)
vmcase(OP_IDIV, /* floor division */
TValue *rb = RKB(i);
TValue *rc = RKC(i);
lua_Number nb; lua_Number nc;
if (ttisinteger(rb) && ttisinteger(rc)) {
lua_Integer ib = ivalue(rb); lua_Integer ic = ivalue(rc);
setivalue(ra, luaV_div(L, ib, ic));
}
else if (tonumber(rb, &nb) && tonumber(rc, &nc)) {
setfltvalue(ra, luai_numidiv(L, nb, nc));
}
else { Protect(luaT_trybinTM(L, rb, rc, ra, TM_IDIV)); }
)
vmcase(OP_POW,
TValue *rb = RKB(i);
TValue *rc = RKC(i);