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Fix divmod and modulo by infinity to match Float#divmod and Float#modulo #429

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Merged
tompng merged 1 commit into from
Sep 13, 2025
Merged

Fix divmod and modulo by infinity to match Float#divmod and Float#modulo #429

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21 changes: 15 additions & 6 deletions ext/bigdecimal/bigdecimal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1733,17 +1733,26 @@ BigDecimal_DoDivmod(VALUE self, VALUE r, NULLABLE_BDVALUE *div, NULLABLE_BDVALUE
*mod = (NULLABLE_BDVALUE) { nan, DATA_PTR(nan) };
goto Done;
}
if (VpIsInf(b.real)) {
VALUE zero = BigDecimal_positive_zero();
*div = (NULLABLE_BDVALUE) { zero, DATA_PTR(zero) };
*mod = bdvalue_nullable(a);
goto Done;
}
if (VpIsZero(a.real)) {
VALUE zero = BigDecimal_positive_zero();
*div = *mod = (NULLABLE_BDVALUE) { zero, DATA_PTR(zero) };
goto Done;
}
if (VpIsInf(b.real)) {
if (!truncate && VpGetSign(a.real) * VpGetSign(b.real) < 0) {
BDVALUE minus_one = NewZeroWrap(1, BASE_FIG);
VpSetOne(minus_one.real);
VpSetSign(minus_one.real, -1);
RB_GC_GUARD(minus_one.bigdecimal);
*div = bdvalue_nullable(minus_one);
*mod = bdvalue_nullable(b);
} else {
VALUE zero = BigDecimal_positive_zero();
*div = (NULLABLE_BDVALUE) { zero, DATA_PTR(zero) };
*mod = bdvalue_nullable(a);
}
goto Done;
}

a_exponent = VpExponent10(a.real);
b_exponent = VpExponent10(b.real);
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20 changes: 15 additions & 5 deletions test/bigdecimal/test_bigdecimal.rb
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Expand Up @@ -2697,14 +2697,24 @@ def test_llong_min_gh_200
assert_equal(BigDecimal(minus_ullong_max.to_s), BigDecimal(minus_ullong_max), "[GH-200]")
end

def test_reminder_infinity_gh_187
# https://github.com/ruby/bigdecimal/issues/187
def test_divmod_modulo_remainder_infinity
pend '-4.2.divmod(Float::INFINITY) is not [-1, Infinity]' if RUBY_ENGINE == 'truffleruby'
BigDecimal.save_exception_mode do
BigDecimal.mode(BigDecimal::EXCEPTION_INFINITY, false)
BigDecimal.mode(BigDecimal::EXCEPTION_NaN, false)
bd = BigDecimal("4.2")
assert_equal(bd.remainder(BigDecimal("+Infinity")), bd)
assert_equal(bd.remainder(BigDecimal("-Infinity")), bd)
pinf = BigDecimal("+Infinity")
minf = BigDecimal("-Infinity")
assert_nan(pinf.modulo(pinf))
assert_nan(pinf.remainder(pinf))
[BigDecimal("-4.2"), BigDecimal(0), BigDecimal("4.2")].each do |x|
assert_equal(x.to_f.divmod(pinf.to_f), x.divmod(pinf))
assert_equal(x.to_f.divmod(minf.to_f), x.divmod(minf))
assert_equal(x.to_f.modulo(pinf.to_f), x.modulo(pinf))
assert_equal(x.to_f.modulo(minf.to_f), x.modulo(minf))
# Float#remainder(plus_or_minus_infinity) returns itself in Ruby >= 3.1
assert_equal(x, x.remainder(pinf))
assert_equal(x, x.remainder(minf))
end
end
end

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