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big: Add div.

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This commit is contained in:
Jeroen van Rijn
2021-07-25 13:25:40 +02:00
parent 2884fa5506
commit c2255c6c19
2 changed files with 72 additions and 36 deletions
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92
core/math/big/basic.odin
View File

@@ -652,6 +652,24 @@ sqr :: proc(dest, src: ^Int) -> (err: Error) {
return mul(dest, src, src);
}
/*
divmod.
Both the quotient and remainder are optional and may be passed a nil.
*/
int_div :: proc(quotient, remainder, numerator, denominator: ^Int) -> (err: Error) {
/*
Early out if neither of the results is wanted.
*/
if quotient == nil && remainder == nil { return .None; }
if err = clear_if_uninitialized(numerator); err != .None { return err; }
if err = clear_if_uninitialized(denominator); err != .None { return err; }
return _int_div(quotient, remainder, numerator, denominator);
}
div :: proc{ int_div, };
/*
==========================
@@ -1014,47 +1032,49 @@ _int_div_3 :: proc(quotient, numerator: ^Int) -> (remainder: int, err: Error) {
*/
_int_div_small :: proc(quotient, remainder, numerator, denominator: ^Int) -> (err: Error) {
// mp_int ta, tb, tq, q;
// int n;
// bool neg;
// mp_err err;
ta, tb, tq, q := &Int{}, &Int{}, &Int{}, &Int{};
// /* init our temps */
// if ((err = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
// return err;
// }
goto_end: for {
if err = one(tq); err != .None { break goto_end; }
// mp_set(&tq, 1uL);
// n = mp_count_bits(a) - mp_count_bits(b);
// if ((err = mp_abs(a, &ta)) != MP_OKAY) goto LBL_ERR;
// if ((err = mp_abs(b, &tb)) != MP_OKAY) goto LBL_ERR;
// if ((err = mp_mul_2d(&tb, n, &tb)) != MP_OKAY) goto LBL_ERR;
// if ((err = mp_mul_2d(&tq, n, &tq)) != MP_OKAY) goto LBL_ERR;
num_bits, _ := count_bits(numerator);
den_bits, _ := count_bits(denominator);
n := num_bits - den_bits;
// while (n-- >= 0) {
// if (mp_cmp(&tb, &ta) != MP_GT) {
// if ((err = mp_sub(&ta, &tb, &ta)) != MP_OKAY) goto LBL_ERR;
// if ((err = mp_add(&q, &tq, &q)) != MP_OKAY) goto LBL_ERR;
// }
// if ((err = mp_div_2d(&tb, 1, &tb, NULL)) != MP_OKAY) goto LBL_ERR;
// if ((err = mp_div_2d(&tq, 1, &tq, NULL)) != MP_OKAY) goto LBL_ERR;
// }
if err = abs(ta, numerator); err != .None { break goto_end; }
if err = abs(tb, denominator); err != .None { break goto_end; }
// /* now q == quotient and ta == remainder */
if err = shl(tb, tb, n); err != .None { break goto_end; }
if err = shl(tq, tq, n); err != .None { break goto_end; }
// neg = (a->sign != b->sign);
// if (c != NULL) {
// mp_exch(c, &q);
// c->sign = ((neg && !mp_iszero(c)) ? MP_NEG : MP_ZPOS);
// }
// if (d != NULL) {
// mp_exch(d, &ta);
// d->sign = (mp_iszero(d) ? MP_ZPOS : a->sign);
// }
// LBL_ERR:
// mp_clear_multi(&ta, &tb, &tq, &q, NULL);
// return err;
for ; n >= 0; n -= 1 {
c: int;
if c, err = cmp(tb, ta); err != .None { break goto_end; }
if c != 1 {
if err = sub(ta, ta, tb); err != .None { break goto_end; }
if err = add( q, tq, q); err != .None { break goto_end; }
}
if err = shr1(tb, tb); err != .None { break goto_end; }
if err = shr1(tq, tq); err != .None { break goto_end; }
}
/*
Now q == quotient and ta == remainder.
*/
neg := numerator.sign != denominator.sign;
if quotient != nil {
swap(quotient, q);
z, _ := is_zero(quotient);
quotient.sign = .Negative if neg && !z else .Zero_or_Positive;
}
if remainder != nil {
swap(remainder, ta);
z, _ := is_zero(numerator);
remainder.sign = .Zero_or_Positive if z else numerator.sign;
}
return .None;
break goto_end;
}
destroy(ta, tb, tq, q);
return err;
}

16
core/math/big/example.odin
View File

@@ -68,6 +68,22 @@ demo :: proc() {
print("quotient ", quotient, 10);
fmt.println("remainder ", i);
fmt.println("error", err);
fmt.println(); fmt.println();
err = set (numerator, 15625);
err = set (denominator, 3);
err = zero(quotient);
print("numerator ", numerator, 10);
print("denominator", denominator, 10);
err = _int_div_small(quotient, remainder, numerator, denominator);
print("quotient ", quotient, 10);
print("remainder ", remainder, 10);
}
main :: proc() {