* ext/bigdecimal/lib/bigdecimal/math.rb (atan): atan(Infinity) is

  PI/2.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@25063 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,4 +1,7 @@
-Thu Sep 24 02:08:35 2009  Nobuyoshi Nakada  <[email protected]>
+Thu Sep 24 02:21:23 2009  Nobuyoshi Nakada  <[email protected]>
+
+	* ext/bigdecimal/lib/bigdecimal/math.rb (atan): atan(Infinity) is
+	  PI/2.
 
 	* ext/bigdecimal/lib/bigdecimal/math.rb (atan): reduce loop with
 	  the formula of the double corner.  based on a patch from

ext/bigdecimal/lib/bigdecimal/math.rb

@@ -117,22 +117,16 @@ def cos(x, prec)
 
   # Computes the arctangent of x to the specified number of digits of precision.
   #
-  # If x is infinite or NaN, returns NaN.
+  # If x is NaN, returns NaN.
   def atan(x, prec)
     raise ArgumentError, "Zero or negative precision for atan" if prec <= 0
-    return BigDecimal("NaN") if x.infinite? || x.nan?
+    return BigDecimal("NaN") if x.nan?
     pi = PI(prec)
-    if neg = x < 0
-      x = -x
-    end
-    if x.round(prec) == 1
-      return pi / (neg ? -4 : 4)
-    elsif inv = x > 1
-      x = 1 / x
-    end
-    if dbl = x > 0.5
-      x = (-1 + sqrt(1 + x**2, prec))/x
-    end
+    x = -x if neg = x < 0
+    return pi.div(neg ? -2 : 2, prec) if x.infinite?
+    return pi / (neg ? -4 : 4) if x.round(prec) == 1
+    x = 1 / x if inv = x > 1
+    x = (-1 + sqrt(1 + x**2, prec))/x if dbl = x > 0.5
     n    = prec + BigDecimal.double_fig
     y = x
     d = y

test/bigdecimal/test_bigmath.rb

@@ -21,7 +21,7 @@ def test_sqrt
     assert_equal(0.0, sqrt(BigDecimal("-0"), N))
     assert_raise(FloatDomainError) {sqrt(BigDecimal("-1.0"), N)}
     assert_raise(FloatDomainError) {sqrt(NAN, N)}
-    assert_equal(PINF, sqrt(PINF, N))
+    assert_raise(FloatDomainError) {sqrt(PINF, N)}
   end
 
   def test_sin
@@ -56,6 +56,7 @@ def test_atan
     assert_equal(0.0, atan(BigDecimal("0.0"), N))
     assert_in_delta(Math::PI/4, atan(BigDecimal("1.0"), N))
     assert_in_delta(Math::PI/6, atan(sqrt(BigDecimal("3.0"), N) / 3, N))
+    assert_in_delta(Math::PI/2, atan(PINF, N))
   end
 
   def test_exp