bigdecimal.c: Fix special cases of BigDecimal#**

[Bug #18677]

Author: mrkn

ext/bigdecimal/bigdecimal.c

@@ -2769,7 +2769,14 @@ bigdecimal_power_by_bigdecimal(Real const* x, Real const* exp, ssize_t const n)
  VALUE log_x, multiplied, y;
  volatile VALUE obj = exp->obj;
 
- if (VpIsZero(exp)) {
+ if (VpIsNaN(exp)) {
+ Real *nan = VpCreateRbObject(n, "0", true);
+RB_GC_GUARD(nan->obj);
+VpSetNaN(nan);
+ return VpCheckGetValue(nan);
+ }
+
+ if (VpIsZero(exp) || VpIsPosOne(x)) {
  return VpCheckGetValue(VpCreateRbObject(n, "1", true));
  }
 
@@ -2858,15 +2865,16 @@ BigDecimal_power(int argc, VALUE*argv, VALUE self)
 
  case T_DATA:
 if (is_kind_of_BigDecimal(vexp)) {
- VALUE zero = INT2FIX(0);
- VALUE rounded = BigDecimal_round(1, &zero, vexp);
- if (RTEST(BigDecimal_eq(vexp, rounded))) {
-vexp = BigDecimal_to_i(vexp);
-goto retry;
- }
- if (NIL_P(prec)) {
- GUARD_OBJ(y, GetVpValue(vexp, 1));
- n += y->Prec*VpBaseFig();
+ if (BigDecimal_IsFinite(vexp)) {
+ VALUE rounded = BigDecimal_round(0, NULL, vexp);
+ if (RTEST(BigDecimal_eq(vexp, rounded))) {
+ vexp = BigDecimal_to_i(vexp);
+ goto retry;
+ }
+ if (NIL_P(prec)) {
+ GUARD_OBJ(y, GetVpValue(vexp, 1));
+ n += y->Prec*VpBaseFig();
+ }
  }
  exp = DATA_PTR(vexp);
  break;

ext/bigdecimal/bigdecimal.h

@@ -283,6 +283,7 @@ VP_EXPORT Real *VpOne(void);
 #define VpSetInf(a,s) (void)(((s)>0)?VpSetPosInf(a):VpSetNegInf(a))
 #define VpHasVal(a) (a->frac[0])
 #define VpIsOne(a) ((a->Prec==1)&&(a->frac[0]==1)&&(a->exponent==1))
+#define VpIsPosOne(a) (((a)->sign>0)&&VpIsOne(a))
 #define VpExponent(a) (a->exponent)
 #ifdef BIGDECIMAL_DEBUG
 int VpVarCheck(Real * v);

test/bigdecimal/test_bigdecimal.rb

@@ -551,6 +551,20 @@ def test_round_up
  assert_equal(-4, m3h.round)
  end
 
+ def test_round_positive_infinity
+ BigDecimal.mode(BigDecimal::EXCEPTION_INFINITY, false)
+ assert_nothing_raised do
+ assert_positive_infinite(BigDecimal::INFINITY.round)
+ end
+ end
+
+ def test_round_negative_infinity
+ BigDecimal.mode(BigDecimal::EXCEPTION_INFINITY, false)
+ assert_nothing_raised do
+ assert_negative_infinite((-BigDecimal::INFINITY).round)
+ end
+ end
+
  def test_zero_p
  BigDecimal.mode(BigDecimal::EXCEPTION_INFINITY, false)
  BigDecimal.mode(BigDecimal::EXCEPTION_NaN, false)
@@ -1492,9 +1506,35 @@ def test_power_with_Bignum
  end
  end
 
- def test_power_with_BigDecimal
- assert_nothing_raised do
- assert_in_delta(3 ** 3, BigDecimal(3) ** BigDecimal(3))
+ data(
+ "BigDecimal(3) ** BigDecimal(3) -> BigDecimal(3**3)" => [BigDecimal(3), BigDecimal(3), BigDecimal(3**3)],
+ "BigDecimal(10) ** Inf -> Inf" => [BigDecimal(10), BigDecimal::INFINITY, :pos_inf],
+ "BigDecimal(10) ** NaN -> NaN" => [BigDecimal(10), BigDecimal::NAN, :nan],
+ "Inf ** BigDecimal(0) -> BigDecimal(1)" => [BigDecimal::INFINITY, BigDecimal(0), BigDecimal(1)],
+ "-Inf ** BigDecimal(0) -> BigDecimal(-1)" => [-BigDecimal::INFINITY, BigDecimal(0), BigDecimal(1)],
+ "BigDecimal(1) ** Inf -> 1" => [BigDecimal(1), BigDecimal::INFINITY, BigDecimal(1)],
+ "BigDecimal(1) ** -Inf -> 1" => [BigDecimal(1), -BigDecimal::INFINITY, BigDecimal(1)],
+ "BigDecimal(0) ** Inf -> 0" => [BigDecimal(0), BigDecimal::INFINITY, BigDecimal(0)],
+ "BigDecimal(0) ** -Inf -> Inf" => [BigDecimal(0), -BigDecimal::INFINITY, :pos_inf],
+ "BigDecimal(-1) ** Inf -> Math::DomainError" => [BigDecimal(-1), BigDecimal::INFINITY, :math_domain_error],
+ "BigDecimal(-1) ** -Inf -> Math::DomainError" => [BigDecimal(-1), -BigDecimal::INFINITY, :math_domain_error]
+ )
+ def test_power_with_BigDecimal(data)
+ BigDecimal.save_exception_mode do
+ BigDecimal.mode(BigDecimal::EXCEPTION_ALL, false)
+ x, y, res = *data
+ case res
+ when :pos_inf
+ assert_nothing_raised { assert_positive_infinite(x ** y) }
+ when :neg_inf
+ assert_nothing_raised { assert_negative_infinite(x ** y) }
+ when :nan
+ assert_nothing_raised { assert_nan(x ** y) }
+ when :math_domain_error
+ assert_raise(Math::DomainError) { x ** y }
+ else
+ assert_nothing_raised { assert_in_delta(res, x ** y) }
+ end
  end
  end