Use common EXCEPTION_INFINITY check in sqrt

Author: tompng

lib/bigdecimal.rb

@@ -147,11 +147,8 @@ def power(y, prec = nil)
   #
   def sqrt(prec)
     BigMath._validate_prec(prec, :sqrt, accept_zero: true)
-    if infinite? == 1
-      exception_mode = BigDecimal.mode(BigDecimal::EXCEPTION_ALL)
-      raise FloatDomainError, "Computation results in 'Infinity'" if exception_mode.anybits?(BigDecimal::EXCEPTION_INFINITY)
-      return INFINITY
-    end
+    return BigMath._infinity_computation_result if infinite? == 1
+
     raise FloatDomainError, 'sqrt of negative value' if self < 0
     raise FloatDomainError, "sqrt of 'NaN'(Not a Number)" if nan?
     return self if zero?

test/bigdecimal/test_bigdecimal.rb

@@ -1383,15 +1383,13 @@ def test_sqrt_bigdecimal
 
     assert_in_delta(BigDecimal("4.0000000000000000000125"), BigDecimal("16.0000000000000000001").sqrt(100), BigDecimal("1e-40"))
 
-    BigDecimal.mode(BigDecimal::EXCEPTION_OVERFLOW, false)
-    BigDecimal.mode(BigDecimal::EXCEPTION_NaN, false)
-    assert_raise_with_message(FloatDomainError, "sqrt of 'NaN'(Not a Number)") { BigDecimal("NaN").sqrt(1) }
-    assert_raise_with_message(FloatDomainError, "sqrt of negative value") { BigDecimal("-Infinity").sqrt(1) }
+    assert_raise_with_message(FloatDomainError, "sqrt of 'NaN'(Not a Number)") { BigDecimal::NAN.sqrt(1) }
+    assert_raise_with_message(FloatDomainError, "sqrt of negative value") { NEGATIVE_INFINITY.sqrt(1) }
 
     assert_equal(0, BigDecimal("0").sqrt(1))
     assert_equal(0, BigDecimal("-0").sqrt(1))
     assert_equal(1, BigDecimal("1").sqrt(1))
-    assert_positive_infinite(BigDecimal("Infinity").sqrt(1))
+    assert_positive_infinite_calculation { BigDecimal::INFINITY.sqrt(1) }
 
     # Out of float range
     assert_equal(BigDecimal('12e1024'), BigDecimal('144e2048').sqrt(10))