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Implement long.__truediv__ through actual long division

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K. Lange 2024-02-27 07:48:15 +09:00
parent 1c75adaa51
commit f75adeb2ca
1 changed files with 64 additions and 11 deletions
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75
src/obj_long.c
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@ -1355,21 +1355,74 @@ KRK_Method(long,__float__) {
return FLOATING_VAL(krk_long_get_double(self->value));
}
static KrkValue _krk_long_truediv(KrkLong * top, KrkLong * bottom) {
if (bottom->width == 0) return krk_runtimeError(vm.exceptions->valueError, "float division by zero");
static KrkValue _krk_long_truediv(KrkLong * _top, KrkLong * _bottom) {
if (_bottom->width == 0) return krk_runtimeError(vm.exceptions->valueError, "float division by zero");
if (_top->width == 0) return FLOATING_VAL(0);
KrkLong quot, rem;
krk_long_init_many(&quot, &rem, NULL);
KrkLong rem, top, bottom;
krk_long_init_si(&rem, 0);
krk_long_init_copy(&top, _top);
krk_long_init_copy(&bottom, _bottom);
/* Perform division */
krk_long_div_rem(&quot, &rem, top, bottom);
/* Take sign from original inputs */
int negative = (krk_long_sign(&top) < 0) != (krk_long_sign(&bottom) < 0);
/* Convert to floats */
double quot_float = krk_long_get_double(&quot);
double rem_float = krk_long_get_double(&rem);
double div_float = krk_long_get_double(bottom);
/* And then make top and bottom absolute */
krk_long_set_sign(&top, 1);
krk_long_set_sign(&bottom, 1);
return FLOATING_VAL(quot_float + (rem_float / div_float));
/* Final outputs that go into the floats */
uint64_t quot = 0;
long long exp = 0;
#define NEEDED_BITS 53
int bits_wanted = NEEDED_BITS;
size_t bits = _bits_in(&top);
for (ssize_t i = 0; bits_wanted >= 0; ++i) {
ssize_t _i = bits - i - 1;
_lshift_one(&rem);
_bit_set_zero(&rem, (_i >= 0 ? _bit_is_set(&top, _i) : 0));
if (krk_long_compare(&rem,&bottom) >= 0) {
if (bits_wanted == NEEDED_BITS) {
exp = 1023 + (bits - i - 1);
}
_sub_big_small(&rem,&rem,&bottom);
quot |= (1ULL << bits_wanted);
bits_wanted--;
} else if (bits_wanted != NEEDED_BITS) {
bits_wanted -= 1;
}
}
#undef NEEDED_BITS
krk_long_clear_many(&rem, &top, &bottom, NULL);
/* Handle rounding? This is probably wrong. */
quot = (quot + 1) >> 1;
if (exp > 2046) {
/* Saturated maximum, but not infinity */
quot = 0x1fffffffffffffULL;
exp = 2046;
} else if (exp < 1 && exp >= -52) {
/* Subnormals */
quot >>= -exp+1;
quot |= 0x10000000000000ULL;
exp = 0;
} else if (exp < -52) {
/* Beyond subnormal, truncate to zero */
quot = 0x10000000000000ULL;
exp = 0;
}
/* Apply sign */
if (negative) exp |= 2048;
/* Mash bits together to form double */
quot ^= 1ULL << 52;
quot |= exp << 52;
union { double d; uint64_t u; } val = {.u = quot};
return FLOATING_VAL(val.d);
}
static KrkValue checked_float_div(double top, double bottom) {