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[ruby/bigdecimal] Let BigDecimal_DoDivmod use the same precision calculation as BigDecimal_divide

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https://github.com/ruby/bigdecimal/commit/11cb2c8840
This commit is contained in:
Kenta Murata 2021-01-22 13:49:46 +09:00
parent e1265c8198
commit 7b2cfce543
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GPG Key ID: CEFE8AFB6081B062
2 changed files with 27 additions and 13 deletions
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33
ext/bigdecimal/bigdecimal.c
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@ -1613,26 +1613,33 @@ BigDecimal_DoDivmod(VALUE self, VALUE r, Real **div, Real **mod)
return Qtrue;
}
mx = a->Prec + vabs(a->exponent);
if (mx<b->Prec + vabs(b->exponent)) mx = b->Prec + vabs(b->exponent);
mx = (mx + 1) * VpBaseFig();
GUARD_OBJ(c, VpCreateRbObject(mx, "0", true));
GUARD_OBJ(res, VpCreateRbObject((mx+1) * 2 +(VpBaseFig() + 1), "#0", true));
mx = (a->Prec > b->Prec) ? a->Prec : b->Prec;
mx *= BASE_FIG;
if (2*BIGDECIMAL_DOUBLE_FIGURES > mx)
mx = 2*BIGDECIMAL_DOUBLE_FIGURES;
GUARD_OBJ(c, VpCreateRbObject(mx + 2*BASE_FIG, "0", true));
GUARD_OBJ(res, VpCreateRbObject(mx*2 + 2*BASE_FIG, "#0", true));
VpDivd(c, res, a, b);
mx = c->Prec * (VpBaseFig() + 1);
mx = c->Prec * BASE_FIG;
GUARD_OBJ(d, VpCreateRbObject(mx, "0", true));
VpActiveRound(d, c, VP_ROUND_DOWN, 0);
VpMult(res, d, b);
VpAddSub(c, a, res, -1);
if (!VpIsZero(c) && (VpGetSign(a) * VpGetSign(b) < 0)) {
VpAddSub(res, d, VpOne(), -1);
/* remainder adjustment for negative case */
VpAddSub(res, d, VpOne(), -1);
GUARD_OBJ(d, VpCreateRbObject(GetAddSubPrec(c, b)*(VpBaseFig() + 1), "0", true));
VpAddSub(d, c, b, 1);
*div = res;
*mod = d;
} else {
*div = d;
*mod = c;
VpAddSub(d, c, b, 1);
*div = res;
*mod = d;
}
else {
*div = d;
*mod = c;
}
return Qtrue;

7
test/bigdecimal/test_bigdecimal.rb
View File

@ -1043,6 +1043,13 @@ class TestBigDecimal < Test::Unit::TestCase
assert_raise(ZeroDivisionError){BigDecimal("0").divmod(0)}
end
def test_divmod_precision
a = BigDecimal('2e55')
b = BigDecimal('1.23456789e10')
q, r = a.divmod(b)
assert_equal((a/b), q)
end
def test_divmod_error
assert_raise(TypeError) { BigDecimal(20).divmod('2') }
end