* math.c (math_log1, math_log2, math_log10): refactoring

  and tests for this.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49979 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 21 insertions, 23 deletions

diff --git a/math.c b/math.c
index 64b38741db..22bd731745 100644
--- a/math.c
+++ b/math.c
@@ -495,7 +495,7 @@ math_log(int argc, const VALUE *argv, VALUE obj)
 static double
 math_log1(VALUE x)
 {
-    double d0, d;
+    double d;
     size_t numbits;
 
     if (RB_BIGNUM_TYPE_P(x) && BIGNUM_POSITIVE_P(x) &&
@@ -507,15 +507,13 @@ math_log1(VALUE x)
 	numbits = 0;
     }
 
-    d0 = Get_Double(x);
+    d = Get_Double(x);
     /* check for domain error */
-    if (d0 < 0.0) domain_error("log");
+    if (d < 0.0) domain_error("log");
     /* check for pole error */
-    if (d0 == 0.0) return -INFINITY;
-    d = log(d0);
-    if (numbits)
-        d += numbits * log(2); /* log(2**numbits) */
-    return d;
+    if (d == 0.0) return -INFINITY;
+
+    return log(d) + numbits * log(2); /* log(d * 2 ** numbits) */
 }
 
 #ifndef log2
@@ -550,7 +548,7 @@ extern double log2(double);
 static VALUE
 math_log2(VALUE obj, VALUE x)
 {
-    double d0, d;
+    double d;
     size_t numbits;
 
     if (RB_BIGNUM_TYPE_P(x) && BIGNUM_POSITIVE_P(x) &&
@@ -562,14 +560,13 @@ math_log2(VALUE obj, VALUE x)
 	numbits = 0;
     }
 
-    d0 = Get_Double(x);
+    d = Get_Double(x);
     /* check for domain error */
-    if (d0 < 0.0) domain_error("log2");
+    if (d < 0.0) domain_error("log2");
     /* check for pole error */
-    if (d0 == 0.0) return DBL2NUM(-INFINITY);
-    d = log2(d0);
-    d += numbits;
-    return DBL2NUM(d);
+    if (d == 0.0) return DBL2NUM(-INFINITY);
+
+    return DBL2NUM(log2(d) + numbits); /* log2(d * 2 ** numbits) */
 }
 
 /*
@@ -591,7 +588,7 @@ math_log2(VALUE obj, VALUE x)
 static VALUE
 math_log10(VALUE obj, VALUE x)
 {
-    double d0, d;
+    double d;
     size_t numbits;
 
     if (RB_BIGNUM_TYPE_P(x) && BIGNUM_POSITIVE_P(x) &&
@@ -603,15 +600,13 @@ math_log10(VALUE obj, VALUE x)
 	numbits = 0;
     }
 
-    d0 = Get_Double(x);
+    d = Get_Double(x);
     /* check for domain error */
-    if (d0 < 0.0) domain_error("log10");
+    if (d < 0.0) domain_error("log10");
     /* check for pole error */
-    if (d0 == 0.0) return DBL2NUM(-INFINITY);
-    d = log10(d0);
-    if (numbits)
-        d += numbits * log10(2); /* log10(2**numbits) */
-    return DBL2NUM(d);
+    if (d == 0.0) return DBL2NUM(-INFINITY);
+
+    return DBL2NUM(log10(d) + numbits * log10(2)); /* log10(d * 2 ** numbits) */
 }
 
 /*
diff --git a/test/ruby/test_math.rb b/test/ruby/test_math.rb
index a4237ecff2..674bb541e5 100644
--- a/test/ruby/test_math.rb
+++ b/test/ruby/test_math.rb
@@ -150,6 +150,7 @@ class TestMath < Test::Unit::TestCase
     check(1, Math.log(10, 10))
     check(2, Math.log(100, 10))
     check(Math.log(2.0 ** 64), Math.log(1 << 64))
+    check(Math.log(2) * 1024.0, Math.log(2 ** 1024))
     assert_nothing_raised { assert_infinity(Math.log(1.0/0)) }
     assert_nothing_raised { assert_infinity(-Math.log(+0.0)) }
     assert_nothing_raised { assert_infinity(-Math.log(-0.0)) }
@@ -164,6 +165,7 @@ class TestMath < Test::Unit::TestCase
     check(1, Math.log2(2))
     check(2, Math.log2(4))
     check(Math.log2(2.0 ** 64), Math.log2(1 << 64))
+    check(1024.0, Math.log2(2 ** 1024))
     assert_nothing_raised { assert_infinity(Math.log2(1.0/0)) }
     assert_nothing_raised { assert_infinity(-Math.log2(+0.0)) }
     assert_nothing_raised { assert_infinity(-Math.log2(-0.0)) }
@@ -175,6 +177,7 @@ class TestMath < Test::Unit::TestCase
     check(1, Math.log10(10))
     check(2, Math.log10(100))
     check(Math.log10(2.0 ** 64), Math.log10(1 << 64))
+    check(Math.log10(2) * 1024, Math.log10(2 ** 1024))
     assert_nothing_raised { assert_infinity(Math.log10(1.0/0)) }
     assert_nothing_raised { assert_infinity(-Math.log10(+0.0)) }
     assert_nothing_raised { assert_infinity(-Math.log10(-0.0)) }